The largest and best supported Jaguar cars enthusiast site on the Internet!

Serving Enthusiasts since 1993
The Jag-lovers Web

Currently with 3,166 members

Electrical System

  Experience in a Book
Electrical System


COLOR CODING: In electrical diagrams, this book uses the same wire color coding scheme as Jaguar uses in their manuals. If two colors are indicated, the first is the base and the second is the stripe. If three are indicated, the third is a spiral stripe. The color codes are as follows:

N - browN (not neutral!) - usually 12V power
B - Black - usually ground
U - blUe
K - pinK
S - Slate (British for gray)
G - Green
Y - Yellow
O - Orange
R - Red
W - White
P - Purple

Jaguar also throws an L in occasionally to indicate a Light color.


WIRING DIAGRAMS: If you're going blind staring at the diagrams in the owner's manual, Michael Frank sends this tip: "Wiring diagrams in the following sizes (prices in British Pounds):

500mmx353mm £9.95 + £1.50 postage
594mmx420mm £12.95 + £2.00 postage
840mmx594mm £19.95 + £3.00 postage
1180mmx840mm £34.95 + £4.00 postage

Available for most classic Jags, with XJ and XJ-S available soon. The diagrams are laminated in plastic and color coded to match the actual wiring. The supplier is:

Classic Graphics
11 Springhill Grove
Stockton, Cleveland TS17 OYW

Dan Jensen adds another option: "I called Jaguar Services (page *)...They stated they have the license to sell copies of the Jaguar wiring diagrams. Price is $20 each for "two-door" models (XJ-S I assume) and "four doors" (S3 I assume) covering the years thru 1987. In later years they apparently have diagrams for each year. They assured me that these were not the wiring diagrams in the owners manual, Haynes, etc., but approximately 25 pages of very specific drawings/details."

Regarding these wiring diagrams, Mike Wilson says, "They now come with a Supplement that includes corrections for the following:

Fig 2.1: Added Diode to Neutral Switch circuit
Fig 2.2: Added Diode to Component location
Fig 6.2: Added Shorting Plug behind Fog Light Relay
Fig 11.1 & 12.1: Corrected the Titles for Coupe and Convertible
Fig 15.1: Ground Code Correction for heated rear window
Fig 20.2: Cruise Control, Resume switch and set switch locations reversed
Fig 22.1: Door Lock Terminal Identification added
Fig 25.1: Added Diode to EFI and Emissions diagram
Fig 25.2: Added Diode component location
Fig 6.1: New wiring diagram for Fog Lamps
Fig 20.1: New wiring diagram for Cruise Control

Both publications are numbered: S-57/90."


OPTICAL FIBERS: If the wire is solid dark gray, it may not be a wire; it might be an optical fiber. Illumination of the air conditioning control panel is via a single light bulb in a housing in the console, with the light carried by fibers to the various locations. This makes the whole panel dark with a single bulb failure, but it's a cinch to replace the bulb; just remove the top cover of the console (3 screws) and replace the bulb inside the housing.

Don't cut those fibers; they're not easy to splice. They are a little brittle, so don't bend them too sharply either. They tend to get in the way when working on the radio, so be careful.

If you need to disconnect one from the fixture at either end, don't just yank. Insert a tiny screwdriver into the slot along the side of the socket and twist to spread it a little, and the fiber will come out easily. It has a little brass fitting on it with a lip. To put it back, simply press it in until it clicks.

Note that the sockets on the bulb housing are not all the same. If you open it up and look inside, you will note that some of the sockets feature a colored filter. Which socket used will determine what color light comes out the end of the fiber.

If you need to try to splice a fiber, Don Mathis of the Lightguide Media Department at AT&T Bell Labs says: cut the ends of your plastic fibers with a razor blade. This should give a very smooth cut. You need to butt the two fibers together while you epoxy them in that position. A "V-groove" works well. If you come up with a means of clamping the two fibers together mechanically, index match grease between the ends helps to decrease the loss. Silicone grease, clear, works well. Vaseline is not bad either.

If all else fails, Edmund Scientific has the fiber for approximately $.70/foot for 0.040" diameter. You can also get genuine Jaguar fibers from several mail order outfits, but they aren't cheap.


WIRE SPLICING: Making durable, reliable wire splices is essential to working on a Jaguar; there are a great many electrical circuits, they tend to be rather complicated, and the Lucas components cause enough trouble. When troubleshooting, it is important to be able to eliminate a previously-made splice as a possible fault.

First, it is helpful to have a pair of wire-stripping pliers around -- a good pair. A good wire stripper will remove insulation from the tip of a wire neatly, doing much less damage to the conductors than you can do with a razor blade, or your teeth, or whatever. However, a cheap wire stripper, especially one in which the stripping slots don't line up properly or are not sharp enough, can cut half the copper strands while removing the insulation.

When splicing wires together, the best way is to solder them -- if they won't be exposed to a great deal of heat, which may melt the solder. A soldering gun of about 140W capacity is recommended; soldering irons are intended for circuit board work, and do not work well doing wire splicing. On larger wires, an iron may not provide enough heat to make a secure connection. And, the intermittent nature of wiring harness repair makes the instant heating of the soldering gun a big help. Even the little light bulbs usually found on soldering guns tend to be helpful in automotive work.

If your soldering gun isn't heating like it should, loosen the nuts holding the tip and retighten securely. These are electrical connections (a soldering gun is a transformer that provides low voltage and high current through the tip to heat it), and they need to be tight.

Regardless of whether the solder used says "resin core", you should use a separate tin of resin flux. The first time you use it, you will know why this is recommended; relying on the resin in the solder doesn't work nearly as well. Do not use an acid flux; it is intended for copper pipe connections, not electrical work. And, before doing any soldering, always dip the tip of the gun in the flux and apply a little solder to the tip as it heats up.

Another workable splicing method, and the method to use when exposure to heat is a factor, is to use a crimp-on connector. If the crimp-on connector is the uninsulated variety, it may be possible to combine methods; crimp the connector to the wires, and then apply solder.

Crimp-on connectors can be purchased in automotive stores, often in a package along with other types of crimp-on terminals. Some of the connectors will have a built-in piece of insulation, while others are bare. Keeping a selection on hand is a must.

Most of the available electrical connectors work well, but there are a couple specific types to avoid. One to avoid is a tap connector that consists of a plastic device than is placed over an existing wire, a new wire is put in place alongside it, a slotted metal guillotine blade connector is squeezed into place with a pair of pliers, and a cover is folded over and snapped in place. While slick, this connector makes weak and unreliable connections, especially on unusual wire sizes.

Where possible, avoid the use of electrical tape. With age, it tends to harden, while the adhesive gets gooey. After some time, tape on connections can be found to have fallen off or slid up the wire, leaving the conductor exposed. If electrical tape must be used, it should ideally be stretched a little as it's applied; the stretch will pull it tightly around the conductors, helping prevent its coming loose anytime soon.

Please don't use friction tape. Electrical tape is solid plastic, while friction tape is black cloth. Friction tape is not intended for electrical work.

If you are connecting separate ends of wire or can slip something over the wire from an end elsewhere, the best insulation method to use is heat-shrink tubing. Heat-shrink tubing is available at some auto supply stores, hardware stores, and building supply stores, but the best place to buy it is at an electronics store. At the better electronics stores it can be purchased in 4-foot lengths and in a great variety of sizes. It also comes in various colors, including near-transparent so you can see how lousy your soldering job was.

Select a size of heat-shrink tubing slightly larger than the insulated wire, and cut a piece a little longer than your splice will be. Slide this piece onto one of the wires before you connect the wires together. After soldering, slide the tubing over the connection and use a cigarette lighter or match to shrink it down snugly. Heat-shrink tubing can also be used to insulate uninsulated crimp-on wire connectors.


CONNECTORS: Since the basic wiring connectors themselves are among the worst features of Lucas engineering, it is recommended that the owner keep a supply of Molex connectors (such as those sold at Radio Shack) on hand. When a connector is intermittent or is otherwise causing trouble, don't try to clean it up; simply cut the sucker off and install a suitable Molex connector in its place.

Some hardware or building supply stores carry a substance for preventing oxidation and corrosion of electrical connections. One such substance is called Ox-Gard, by Gardner Bender Inc. of Milwaukee; it comes in a 1 oz. tube and has the consistency of grease. Since Jag electrical connections tend to corrode, it is suggested the owner keep a tube of this stuff around and use it. The first place to apply it is on both ends of each fuse you can find.

Tom Wagner says, "I have a number of associates that actually grease the lamp socket base. They swear that it keeps the moisture out and prevents rust. I have no emperical data to confirm this and really don't have the guts to try an experiment. I have noted however that some cars (especially Fords) have a type of white grease packed into the connectors. Unfortunately every time I have seen this material it is because I have been replacing the device, so I don't know if the device has failed due to it or whether it is just a normal failure."


GROUNDS FOR COMPLAINT: This author has noted several places in the XJ-S where a ground connector is attached to the chassis with a bolt or screw that also holds a harness strap. The harness strap is plastic, and is held between the ground wires and the chassis. This is NFG for at least two reasons: First, it means that the only way the ground connection can possibly be made is through the screw itself, which is less than half as reliable as a properly seated ground connection. Second, since the strap is plastic, the screw simply cannot be tightened securely, as that would only crush the strap.

The car has enough electrical problems. It is recommended that whenever such a ground connection is found, it should be revised. One method is to provide two separate screws, one for the harness strap and one for the ground. Be sure to scrape all the paint away under the ground connection before reinstalling it. Maybe a little anti-seize compound would help, too -- both in assuring a good electrical connection and in keeping the bare metal from rusting.

So far, such ground connections have been noted on the wheel wells just behind the headlight housings on both sides, and inside both doors near the hinge end.


SPADE TERMINAL INSULATION: In the places that the XJ-S has female spade terminals to connect to male spade lugs on a device -- such as on the starter relay at the right rear corner of the engine compartment -- the female terminals on the ends of the wires have a milky white plastic sleeve that snaps in place over the terminal to prevent accidental shorts. These insulators are guilty of misleading in two different ways: 1) When the terminal is pushed onto the spade lug on the device, the lug may enter the insulator between the flat side of the terminal and the sleeve rather than into the terminal itself. This may actually feel like it was inserted properly, and will usually provide a connection when tested -- but it will be intermittent, and you will have problems sooner or later. 2) When the connector is pushed onto the spade lug, the terminal itself may slip backwards within the insulator without being noticed. It looks like it's in place, but the terminal itself is actually only touching the tip of the spade lug, again making an intermittent connection.

A very workable plan is to take these insulators off and throw them away, and insulate the female spade terminals using heat-shrink tubing.

If you are installing new female spade terminals on a wire, it is suggested that you use two different sizes of heat-shrink tubing to insulate them. This works far better than the little plastic collars that come on crimp-on terminals, so it is suggested you rip the plastic collars off and use this method instead. This also allows you to solder the wire to the terminal after crimping for a more secure electrical connection. To insulate the terminals, take a piece of heat-shrink tubing about 1/2" long and a diameter that will fit over the wire itself as well as the crimp end of the terminal and slide it onto the wire before attaching the terminal. After crimping and soldering, slide this piece over the crimp connection and use a match to shrink it down onto the crimp itself, leaving just the spade terminal exposed. Then cut a piece of heat-shrink tubing of a diameter that will fit over the female spade terminal itself about 1/2" long and slide it on until the end is flush with the business end of the terminal, and shrink it in place so that it covers the terminal and overlaps the first piece over the crimp. The end result is a two-level insulation job that looks professional and even provides a measure of strain relief to the wire connection.

It's possible to do a similar two-level insulation job to a male terminal using a very short piece of the larger heat-shrink tubing, but it doesn't surround the terminal itself when disconnected, so unplugged terminals involve some risk of bumping into things and shorting. It works just splendidly when plugged in, though.


CONTACTS: Vince Chrzanowski of Baltic, CT restores old auto radios for a living. He recommends Channel Master COLOR contact Shield, Silicone Base, which is available at most electronic supply houses. Model 9101 is the 16-oz. can; model 9100 is a 6-oz. can of the same stuff. He claims many rocker switches, even many of those that appear to be broken, can be fixed by spraying this stuff through the cracks without even removing the switch from the panel!

Chad Bolles likes LPS 1. "It is greaseless and does not attract dirt and is made for elec systems." Tom Wagner adds, "CRC has a chemical for cleaning too."

Tom Wagner warns against confusing electrical contacts with connectors, and using the wrong product: "My major concern is that folk will generically use contact cleaners without actually knowing that fuses and the like are actually connectors. Never, I repeat, never use a contact cleaner on them. They are for rotary switches and will do more damage than good. Often a cleaning with alcohol and a clean business card is all that is needed. There are chamois on sticks for cleaning VCR heads at Radio Shack that are excellent. Never use a Q-Tip, they will leave material behind. For pin connectors, clean all the dirt you can out and use alcohol followed by air to take any surface residue out. Then a simple repeat removal and insertion of the connector a number of times is often all that is needed. Stubborn cases usually require more drastic means. A typewriter eraser used gently is a very good burnisher. Round wood toothpicks can be used to clean the female part of sockets.

"Check for broken or cracked parts. They can also show where failures might be; the electronic circuits very seldom break down, but sometimes the plastic they are attached to allows the connections to fatigue, resulting in poor connections."


EFI CONNECTORS: The connectors that snap onto the fuel injectors and the temperature sensors are rectangular, hard, and have an external spring to provide snappage. These connectors, used on Bosch and Lucas systems worldwide, are common enough that replacement connectors are available.


POTENTIOMETERS: Tom Wagner says, "There is another product for variable resistors like volume controls and air position sensors. It is a pretty good "stop gap" solution for intermittant radio controls and sensors, but has to be sprayed directly on the carbon track. It does work, have used it for years on noisy radio controls. Check the can and be sure that it is for controls not switches. In the old days we used "carbon tetrachloride" (just tapped the shop fire extinguisher), but that wrecks your liver and can actually be absorbed through the skin. Illegal and dangerous!"


WIRING HARNESS RENOVATION: Richard O. Lindsay sends this innovative method: "Tie the harness into position with tie-wraps thereby preserving all of the original bends and more importantly, break-out points. Remove all of the jacket leaving the wires only in position. This is a good time to clean and degrease all of the insulation. Then cut each wire, one at a time, about a foot or so back from the connector end. This cut should be well back into the jacket away from the breakout point. This allows you to splice in a piece of generic wire of the appropriate gauge and turn the original cut off wire around leaving the nice clean color-correct wire sticking out. The addition of a correct connector makes for a functional harness that, when vinyl wrapped, will look new and be color code correct!"

Dave Covert sends the following: "The cloth cover is not something you can really buy, but must send your harness to a shop and have it wrapped. The shop has a braiding machine that weaves 32(?) strands of cotton thread around the bundle. Sixteen strands in a clockwise direction, sixteen strands in a counter-clockwise direction. The cotton strands are usually black, but if your original harness had a colored tracer thread(s), send a sample along with the harness and the shop will switch some of the 32 strands out for colored strands to match the original tracer. The shop will also want you to mock up your harness with a few pieces of electrical tape to hold it in the proper shape.

"Cost is modest, and varies a bit from shop to shop. I had good conversations with two different shops, each with different pricing schemes. The first shop was Class-Tech of Bend, Oregon, 1-800-874-9981. The second shop was Harnesses Unlimited of Oreland, PA, (610) 688-3998."

If a complete rewrap isn't called for, Bruce Snyder sends these suggestions: "I've had a lot of success with the large sizes of heat-shrink tubing available at electronics suppliers. It's available in long lengths and a large variety of diameters, and looks quite nice when installed. Of course, you have to be able to slip it over the wires. The other thing that has worked well for me is the dry vinyl and cloth wrapping tape from Eastwood, and the cold shrink tape. These work very well, and have no adhesive to make that sticky mess we all love so well. These all take a little time to install, but look good, are durable, are considerable cheaper than a new harness and don't involve extricating the old harness for re-wrapping."


RODENT DAMAGE: One of the members of the XJ-S online discussion group happened to mention that his wiring had been damaged by rodents, and it was simply amazing how many members responded with similar experiences! Apparently Lucas wiring, along with all its other shortcomings, is found delectable by rats! The problems usually seem to occur up in the V between the heads; it's probably a nice, warm, cozy spot for a rat to curl up in, and there's an assortment of tasty wires to chew on. Simon Gray reports, "I spent yesterday replacing spark plug leads, you guessed it, mice. It may have been a rat, either way it took one night to eat through four cables and totally ruin my day (I had renewed them three months ago)." They don't limit themselves to spark plug leads, though; there are also reports of chewed fuel injection wiring and ignition pickup wires.

Matt Dillon suggests, "My solution was to leave a cheap radio on in my garage all the time. Apparently the mice don't like the noise. My radio's been on for 2 years without any further rodent attacks. Until I started playing the radio, my cat was attacked twice!!!"

Perhaps you should get a cat to protect your cat, Matt.


FUSES: The UK uses a different definition of the rating for fuses than the US does. The US rating is for how much current the fuse will carry without blowing; the UK rating is for the amount of current to blow the fuse within a certain time. The difference is about 2:1. Simon S. Johnson sends the following data: "...the source: a 1974 edition of "Buss Fuse Car and Truck List" which has on the back cover a section call "Foreign Car Fuse Replacement Data," -- foreign to the US, that is. It states that "English standards differ from US standards. This accounts for difference in ampere ratings." Then it provides a list:


English Type

Buss Replacement

50 amp

AGC 30

35 amp

AGC 25

30 amp

AGC 20

25 amp

AGC 15

20 amp

AGC 10

10 amp

AGC 7 1/2

5 amp


You may find that your fuses have a little paper label inside with both ratings; a Lucas rating (British) and a "continuous" (American) rating.

If your car uses tubular glass fuses and the repair manual specifies an amperage, it's in the British rating; you will have to correct per the chart above to use the correct American fuse.


RELAYS: There are relays all over the XJ-S. Most are a Bosch 12V 30A SPST relay number 0 332 014 113, and are a small metal box with spade terminals labeled 30/51, 85, 86, and 87. 85 and 86 are the coil connections, 30/51 is the common contact, and 87 is the Normally Open (NO) contact. The typical layout of these terminals is shown in Figure 24.

These relays conform to a standard, and are readily available at any auto parts store. Often, the aftermarket relays are labelled for use in controlling driving lights, and may be found among the driving light kits instead of under general electrical components. They are usually entirely black plastic, and they often have an integral mounting lug. And of course, an aftermarket electrical device is likely to be as good or better than a British original (although not all -- this author found a particular type relay made in Italy and sold at AutoZone that wasn't worth a damn, three in a row failed quickly).

Some of these relays (and some of the aftermarket generic equivalents) have a second terminal 87 in the center of the base. This terminal is connected internally with the first 87; it merely serves as a second terminal to the same contact. In most cases, a relay with the extra spade terminal can be used to replace a relay with only one 87, as the socket or plug will have a hole or slot for the unused spade to protrude through. However, one should be careful about replacing a relay with two terminals with a relay having only one; the socket may have a wire that connects to this spade, and will not be connected if it is not there. At this point, the solution is usually a simple matter of trading one relay with another to get a relay having both terminals where it is needed.

If you are installing or relocating relays, you should note that relays are not watertight, even when they appear to be. Their durability will be greatly enhanced if you will install them with the terminals pointing downward, so that dripping water can't get in and any moisture that does get in can drain out. Bosch relays even have a little hole in the bottom that you can use to spray contact cleaner or some such in there to help keep things from getting cruddy.

Unfortunately, the XJ-S is covered with exceptions to the relay standard. Following are descriptions of several components that look like standard relays and will fit in the standard socket, but are not the same and exchanging with standard relays may cause problems or even shorts.


RADIATOR FAN RELAY: This relay, SRB411, has the exact same layout of spade terminals on the bottom, except that the terminal in the center is labeled 87a. This relay is bright red -- Lucas' way of indicating "Hey, dummy, this relay is different!" A close inspection of the schematic on the housing shows that this is in fact a SPDT relay, and the 87a is a Normally Closed (NC) contact.

In this particular application the 87 contact is 12V power and the 87a contact is connected directly to ground. As a result, if a normal relay with two 87 terminals is plugged in, a direct short will result and fuse #1 in the headlamp fusebox will blow immediately.

The NC contact shorts the fan motor to ground when not operating. It's not known why Jaguar did this. If a normal relay that has no center spade terminal is installed, the system seems to work fine; the fan operates normally when on, and the fact that the fan is not grounded when off doesn't seem to make any noticeable difference. However, it seems unlikely that Jaguar would have gone to the effort of supplying the grounding circuit without a good reason.

Even though a generic driving light relay won't serve here, finding a 12V 30A SPDT relay is usually not too difficult. If you don't wish to buy the Lucas original, you can look for a Bosch, Hella, or Potter & Brumfield. Per Bob Whiles, the part number for the Bosch is 0 332 204 105 and for the Potter & Brumfield is VF4-45F11; this author suspects Bosch numbers 0 332 204 109 and 0 332 204 125 would work as well. Per Volker Nadenau, the Hella part number is 4RD003 520-13. All of these will plug right into the red socket. Of course, finding a parts store employee here in Florida who even knows what a relay is, much less whether or not it has NC contacts, can be a challenge; "What kinda car is that fer?" as he prepares to type on his computer terminal. Actually, the best place to look for relays is in a junkyard; just about all cars use relays for one thing or another, although they are usually hidden inside fuseboxes or other compartments. European cars often use Bosch relays. All automotive relays seem to have a little schematic on the outside, so it is a simple matter to confirm whether or not a relay has the necessary 87a NC contact.

Or, you can go to an electronics store and buy a generic "ice cube" 12VDC SPDT (or DPDT, 3PDT, 4PDT, etc.) and solder short jumper wires to suitable spade connectors to plug into the original socket. If you get extra contacts, just wire them all up to provide extra current capacity.


87b: Some relays, including Bosch number 0 332 015 006 and 0 332 015 012, have an 87b terminal. This is a second NO contact just like the 87 terminal. However, while the relays with two 87 terminals have both terminals connected to the same contact, this relay actually has two separate contacts. Here's the distinction: when the relay is energized, the same connections are made as in the relay with two 87's, but when unenergized, the 87 and 87b terminals are not connected to each other. In some instances, this may make no difference, and perhaps a relay with an 87b terminal can be used to replace a relay with two 87's, but be very careful replacing a relay with an 87b with a relay with two 87's -- something might backfeed through the 87 terminals on the relay and cause malfunctions.


ELECTRIC FAN DIODE PACK: Yet another exception to the typical relay described above is the blue item mounted on the top left side of the engine compartment just rearward of the diagonal strut. It looks like a standard relay, and has the same spade terminal layout as a standard relay, but it's not a relay at all; it's the diode pack for the electric fan. The terminals are numbered simply 1, 2, 3, 4, and 5. You can easily pry the box open with a small screwdriver and inspect the layout inside.

Diodes merely allow current in one direction only. When testing this pack, you should be able to get current to flow from terminal 3 to terminal 1 but not the other way around. You should also be able to get current to flow from terminal 5 to terminal 4 and from terminal 2 to terminal 4, but not the other way on either. This description uses the accepted definition of current as flowing "from" a + terminal to a - terminal. Note that some meters may not incite a diode to flow in either direction when set to a standard ohmmeter setting; if the meter does not have a setting for testing diodes, it might be better to use a light bulb to test.

If any of the diodes prove bad, it's not rocket science to replace them individually. Suitable diodes are available at any electronics supply store; Radio Shack catalog number 276-1661 will serve nicely.

In case you haven't developed a healthy disrespect for Lucas engineering yet, here's another example of their handiwork: the wires that connect to terminals 1 and 3 are both GN, but they are different and you'd better not mix them up! Likewise, the wires that connect to terminals 2 and 4 are both LG, but don't mix those up either!

If you've already disconnected them and gotten confused: on the author's 1983 XJ-S, the GN wire that connects to terminal 1 is actually two wires connected to the same spade terminal, while the GN that connects to terminal 3 is a single wire. Likewise, the LG wire that connects to terminal 2 is actually a pair of wires, while the LG that connects to terminal 4 is a single wire. Here's hoping other cars are the same!

I will describe more elaborate tests, in case the above proves inadequate. If you apply 12V to a GN wire and the fan starts running, that wire connects to terminal 1. If the clutch on the A/C compressor engages, it connects to terminal 3. If the engine is cold and you turn the ignition on and read 12V at a LG wire, it connects to terminal 2; if not, either a fuse is blown or it connects to terminal 4.

Just when you thought you had these things figured out, Jaguar goes and does something totally unexplainable. Michel Carpentier reports on the diode pack in his Daimler Double Six: "The blue box is clearly the same as described in your book: one diode with anode in 3 and cathode in 1; two diodes with anodes in 2 and 5, common cathode in 4. But it provides the logic for the headlamp wash/wipe system. 2 is connected to a blue/red wire (high beam), 5 to a blue/white wire (low beam), 4 goes to terminal 85 of the wash/wipe relay via a blue/red wire. 1 has a green/blue wire going to one of the washer pump terminals. 3 has two green wires, live when ignition is on. Terminal 86 of the headlamp wash/wipe relay is connected to the other terminal of the washer pump (common to windshield and headlights) and to the windshield washer switch. When you push the windshield washer switch, terminal 86 of the headlamp wash/wipe relay is grounded and the pump operates via diode 1/3. If the headlights are off you get normal windshield washer operation. If they are on (either low beam or high beam) 4 is live so the relay is energized: the headlamp wiper motors kick in and valves open, squirting fluid on the outer headlights. Much ado for a perfectly useless gadget!

"Back to the cooling fan. Against the radiator is a small harness which comprises the following: A green/brown wire running from a connector on the RHS of the radiator (said connector linked to A/C compressor clutch) to terminal 86 of the red fan relay. Somewhere in between, this wire is cut and a small PCB (about 30x8mm) holding a diode soldered in, with the cathode towards the relay. Terminal 86 of the red fan relay is also connected to the thermostatic switch by a green/white wire. A black wire connects terminals 85 and 87A to ground. A brown/green wire comes from the main harness on the LHS (live at all times) and goes to terminal 87. Another small PCB (exactly 32x10mm) is also buried inside the harness. It holds two diodes with a common cathode connected to the thermostatic switch by a green/orange wire. One anode has a red wire going to terminal 30/51 and thence to the fan motor. The other anode is connected to the main harness by a green wire (live when ignition is on). This harness is held together by the usual weaving: outwardly there is no way you can tell that it is so electronically sophisticated as to contain 3 diodes!"


EFI MAIN RELAY: On the Digital P EFI system diagrams, item #312 is the "main relay". This relay is mounted in the trunk near the ECU, right alongside of the fuel pump relay. Don't mix up the two relays; the fuel pump relay is a standard relay, but the main relay, Bosch # 0 332 014 112, looks like a standard relay, but it has a diode installed internally in series with the coil. This difference is clearly indicated on the little schematic embossed in the side. They also paint a colored diagonal stripe across the top to indicate it is unusual.

Ironically, in this case making a special relay was totally unwarranted; a normal relay can be used by simply adding a suitable diode (such as Radio Shack catalog number 276-1661) in the wiring to the coil.


FEEDBACK MONITOR RELAY: On the Digital P EFI system diagram for the North American "Emission A" spec, item #355 is the "feedback monitor relay". This relay is mounted under the black plastic cover at the right rear corner of the engine compartment, alongside the starter relay and the cold start relay. The cold start relay is a standard relay, but the feedback monitor relay is anything but -- don't mix them up. The feedback monitor relay, Bosch #0 332 014 411, has a diode mounted internally in parallel with the coil. Beyond this difference, however, is the fact that the connections on the base are rearranged, with one of the coil terminals and one of the contact terminals being reversed compared to standard relays. The schematic embossed in the side shows the component clearly, and there is a diagonal paint stripe across the top to indicate it is unusual.

The feedback monitor relay is illustrated in the schematics as a normal relay. It's not known if some earlier cars use a standard relay here.

There was no real need for a special relay here; a normal relay with an external diode (such as Radio Shack catalog number 276-1661) would work fine. If you choose to substitute, however, be sure to rearrange the terminals in the socket to the standard relay positions.

Editor's Note: As a professional Mechanical Engineer, I have to express an opinion here: the guy who decided it was a good idea to make several totally different and non-interchangeable components all fit in the same socket should be stood up against a wall and shot. There is simply no excuse for this level of incompetence.


LATE MODEL RELAY PROBLEMS: Michael Neal warns: "I just wanted to advise the list of a known problem with late model Jags, roughly '93 and later. They have several Hella brand relays in various places for different components. Underhood usage of them seems to be the worst problem. The XJ-S and XJ6 use them extensively on everything from A/C clutch control to EFI main relays. Hella apparently came out with a replacement to "fix" the failures. They haven't been working. Whenever I have a strange problem come in, 90% of the time it's been one of these damn relays. Unfortunately I'm forced to replace them with what Jaguar provides so that's what they get. The relays are developing bad contacts and overheat, failure is usually intermittent. Most of these relays have a light blue case. You can troubleshoot them by pulling the relay and jumping between the 30 and 87 terminals."

Leonard L. Peake adds, "There is a Jaguar "Service Bulletin" in regards to all relays on 1993 cars that have a date code before "183" stamped on the side."


STARTER RELAY: Dick Broxon of Cincinnati reports that his '88 XJ-S would fail to start on damp mornings. It wouldn't even turn over, it would just click. It would start later, though, when things had warmed up and dried out. He removed the plastic cover from the relays under the hood on the right fender and sprayed them with a product called WIRE DRYER by Snap. He has not had a problem since.

The starter relay, of course, is under the cover mentioned. It carries more current than most relays, and a little moisture or corrosion is likely to cause the starter solenoid to fail to move.




STARTER: Greg Meboe and Michael Neal report that Jaguar provided a new design starter beginning in 1988 that features a gear reduction drive. This starter will fit earlier V12's, and is smaller, lighter, more reliable, and just all-around better.


STARTER REMOVAL: Both the Repair Operation Manual and the Haynes manual list several steps involving the steering column. This must reflect RHD cars; you don't have to mess with the steering column at all in a LHD car.

David Johnson wants everyone to be aware that the upper bolt holding the starter in has a 12-point head, and therefore requires a 7/16" 12-point socket. The manuals simply say to remove the bolts. "You can't really see the bolt head even with a mirror. So because most bolt heads are 6 point, I tried for what seemed like days with several different size sockets."

"Also I learned not to remove the transmission dip stick and tube. What a mess! I guess with the car up on ramps the fluid ends up being significantly higher than the bottom of the tube."


STARTER SLOW TURNING: Mike Morrin: "Check that the engine grounding cable (underneath on the left hand side) is not loose or damaged. This is not particularly an XJ-S fault, but it was loose on mine, and I would have been really mad if I had pulled the starter before discovering it."

The fact is that lots of electrical gremlins have been traced to faulty grounds, a lot of them to this strap in particular. As a preventative measure, it might be a good idea to simply buy another engine ground strap and add it to the car, connecting it to anyplace on the engine and anyplace on the chassis.




ALTERNATOR: The experts advise that if there is any indication that your alternator is having trouble (not charging, low voltage, etc.) that you have it attended to immediately. If caught soon enough, it can be repaired or rebuilt. If left alone, it self-destructs and a new one is required.

Reportedly, one indication your alternator has had it is that the alternator warning light stays on after the engine is shut off.

One bit of good news: If the alternator seems to be charging intermittently (fully charging one minute, discharging the next as indicated by the voltage gauge) or has simply stopped charging but has no shorts or burnt wiring, it might be fixable by replacing just the regulator itself. This is much cheaper than replacing the whole alternator, and is easy to do by removing the plastic cover from the back of the alternator.

A replacement Lucas or Bosch alternator is quite expensive, but a bolt-in substitute apparently does not exist; the mount scheme is different than GM alternators, a Chrysler alternator won't come close to fitting in the space, and several Japanese units will bolt up but the belt will be misaligned. Of course, another possibility involves making an entirely new mount to fit whatever alternator is available. Any 12-volt internal-regulator alternator of comparable or greater amperage would serve if it could be mounted. However, the mount on the engine is rather convoluted and is involved in mounting the air pump as well, so it is no easy task to fashion a replacement. Note that the cost of a new Lucas alternator would pay for a GM alternator and a very expensive custom-made bracket, and the next replacement would be cheap.

John's Cars offers a bracket to fit a GM Delco alternator, complete with a suitable wiring connector. Michael Minglin says, "A little pricey, but well-designed and went in without any problems. Now have 100 amp 12SI alternator for less than $200 total." Minglin opted for a beefed-up Delco alternator; "The main modification was heavy duty heat sinks because of the high underhood temperatures."

If removal of the air injection system is a viable possibility, you might consider the procedure described in the section on Engine Modifications.

Also note that there are reports of Motorola alternators that fit this car, and possibly even fitted from the factory. Bob Johnson says the number is A5000/12.

Beginning with engine #8S57572, the series of Lucas alternators was replaced with a Bosch 115-amp unit. According to the Special Interest Car Parts catalog, the alternator mount bracket EAC4181 was replaced with EAC9320 at the same time. Perhaps the purchase of this bracket will permit the upgrade of the earlier cars to the Bosch unit. Since they all use internal regulators, the wiring connections should be fairly straightforward.

Also, the 115-amp alternator is driven by a flat multi-groove belt instead of the V-belt found on earlier cars. Since the alternator is driven from the crank damper itself rather than from the pulley that bolts onto it, this change involved the replacement of the earlier crank damper C36013 with one with the multi-groove layout, EAC9248 (replaced sometime thereafter with EAC9693 to fit a timing disk for the Marelli ignition). The pulley part number doesn't change. So, if you retrofit the 115-amp alternator to the earlier car, you can either purchase and install a new crank damper, or you can simply replace the pulley on the 115-amp alternator with a V-belt type. Note that there may actually be some problem with this latter scheme; historically, alternators driven by a single V-belt never exceeded 60-70 amps or so, larger alternators used two V-belts prior to the introduction of the multi-groove belt.

Scott Horner of New Zealand retrofitted the Bosch alternator to his UK-spec pre-H.E. XJ-S; note that this car never had an air pump, so the alternator mounting may be considerably different than US-spec cars. "The Bosch alternator is bigger than the Lucas and Motorola in most dimensions. This meant having to drill out the original mounting bracket ëswing' (technical term!) hole, definitely needs to be done using a drill press. Trying to find a replacement pivot bolt with a larger diameter was entertaining; I eventually got a suitable bolt from a motorcycle store (but that could just be good old NZ and the complete lack of parts).

"The unit I got had a grooved belt pulley originally (although the Jaguar parts manual lists both grooved and V-belt) so I had to remove this and fit a normal V-belt pulley. The shaft size on the Bosch is larger than the Lucas and Motorola, so you can't use the original. I was lucky enough to be able to rummage through a collection of dead Bosch alternators, which all have the same shaft size, and found a suitable replacement, even down to the offset (so the belt lined up with the crank pulley).

"I was able to re-use the original power connectors on the back of the alternator (although I had to drill these out as well to make them fit)."

Regarding the whole general idea of replacing one alternator with another, John Napoli offers some wisdom: "It is a good idea, IMHO, to go with a common alternator for your geography. Volts are volts, what you want is dependability and maintainability. A large Lucas infrastructure exists in Britain. In the US, a large infrastructure exists for GM stuff. The same can probably be said for other marques, but I have GM experience, and there is no shortage of ridiculously cheap GM components in the States!"


ALTERNATOR EXCITATION: The field on the XJ-S alternator is excited through the warning light, so if this light is burnt out or disconnected charging may be intermittent. According to Randy Wilson, "A common enough design. Lots of alternators will respond like this... some would never charge. Here's what happens: the alternator needs a signal to indicate the key is on, and a power source to boost itself into a charging condition... bootstrapping, if you will. This power requirement is low enough that a lot of alternators use the power flow through the charge light for this purpose. This is called the exciter. And, in reality, key on is not really an important condition to the alternator. You just don't want to be driving the exciter full time, lest your battery will go flat overnight. Once the alternator is charging, it becomes self-exciting, and no longer needs or uses this external power source (oversimplification). Thus the light goes out.

"The exciter is used to induce enough of an electromagnetic field to start the current generation. However, there is always some residual magnetism floating around in a used alternator. With this residual, the alternator can generate a little bit of current, if you spin them fast enough. In the case of Lucas (and others) the current needed to self-excite is fairly low -- low enough that the current from the residual magnetism can meet the demand. This usually happens at 2500-3000 engine rpm. And as soon as the alternator is up and charging, operation is as normal. You don't have an outside exciter source, but you don't need it any more.

"The moral of all this is that silly charge system idiot light is a double-sided test. Everyone knows it is bad when the light is on with the engine running. Few people know that it is equally bad if the light stays off with the engine not running, but the key is on."


ALTERNATOR TROUBLESHOOTING: Michael Minglin says, "I really like the factory manual's instructions for checking maximum amps output. Even If I could reach down there to remove the plastic cover, I could not see to connect a jumper between "F' and "-". My solution was to remove the alternator and attach wires from "F" and "-" and run them out of the back of the alternator, up the inside of the fenderwell, with a male and female connector on the end by the cross brace. Now to jump the regulator all I have to do is connect the connectors. I'm not sure it is worth pulling the alternator just to make these connections, but I will never put in another alternator without this modification."


ALTERNATOR LOAD DUMP MODULE: Reportedly, the 115-amp alternators fitted to the late 80's XJ-S will not begin to charge until the engine has been revved up. Although not really a problem, it is somewhat irritating to see the charge light on when everything else seems OK. According to Michael Neal: "Actually, there is a fix for this. There is a device called an alternator load dump module that was fitted to the later XJ40's and XJ-S's with the high output alternator. Fitting the module will fix the problem. The load dump module will cause the alternator output to function properly at idle without having to raise the idle speed." The part number for the 115-Amp dump module is DBC 5896.




BATTERY: When your battery needs replacing, you will find that the XJ-S uses an unusual battery -- and that Jaguar wants $$$$ for it. The Jaguar battery comes with an enclosed vent connected to a tube to route the vent out through the floor of the trunk. Batteries are normally in engine compartments which are well ventilated, and things still corrode right around the battery. A trunk is not ventilated at all, so the battery vapors will corrode the whole trunk. Harry Trafford reports: "the DPO let the Jag dealer in Miami install a new one. The dealer installed a standard Interstate mega-something and charged him $150 US for a $59 battery! The thing out-gassed into the boot and now I have a major rust repair job ahead of me. And no, the little red plastic Jaguar vent cover does not work. There are large rusted out areas up in the buttresses and along the boot area on either side of the lid, including the area between the rear glass and boot lid. The only thing keeping out the rain is the paint. Push a finger into any of those places and you'll be looking at the spare tire. We're not talking pinholes here."

Worse yet, batteries emit hydrogen gas when charging, so you run the risk of blowing the trunk lid off your car.

According to Randy Wilson, an Audi 5000 battery (Audi put the battery in the passenger cabin, so it has similar venting provisions) will fit with the addition of a half inch plywood shim.

Wilson also reports that Interstate offers an add-on vent kit for their batteries. And there are some marine batteries with vent provisions.

Charlotte Hand reports that the make of batteries sold at Pep Boys, Pro Start, offers a "group size 34" battery for the XJ-S, complete with the proper vent provisions. There are apparently at least two to choose from, the cheapie and the high end.

Robbin Lewis says, "Sears now sells an "International" DieHard Battery that is an almost exact match to the original Jaguar battery, but at a much cheaper price. The only thing I had to do was move the 90 deg. fitting from the right side to the left... easy to do. Just swap the blank plug on the left side with the angle fitting on the right."

Delco Freedom batteries, as well as some Champion batteries, come with a flat top vent/cap assembly that has a vent opening on each end. Each is sort of a flat oval shape, but it is possible to connect tubing to them. Hopefully this is a trend among battery manufacturers; being able to remotely vent batteries is a plus, and it can't cost them much to provide the capability. Other Champion designs -- many of which are alongside on the same shelf, sometimes sharing the same part number -- have obscure venting, apparently coming out of whereever around the vent caps, and clearly impossible to properly seal.

A flat-top Champion model 78-2 fits the '83 XJ-S perfectly. It is a simple matter to fashion a suitable vent scheme with some 1/4" ID clear vinyl tubing and a plastic tee. This battery comes with an 84-month warranty, 24 month free replacement, 36 months free jumpstart, and is rated at 950 cranking amps at 32F and 770 cold cranking amps at 0F.

The catch? Model 78-2 is a side-terminal battery! The original top-terminal cable ends must be cut off and side-terminal cable connectors installed. They cost only a coupla bucks, the cost is no big deal. In truth, the XJ-S looks like it was designed for side terminals; there is precious little room for top terminals, requiring an unusually short battery height-wise. There's plenty of room on the front, however, and use of side terminals allows this full-size battery to fit under that plastic cover.

A more traditional design battery can be made to serve, but you must find a way to vent the fumes outside of the trunk. Find or make a cover to completely enclose the vents on the top of the battery (being selective when you buy the battery may help here), or an airtight container for the entire battery. Connect a vent tube and run it out through the floor of the trunk. B. J. Kroppe suggests "install a DIN cover over your battery. (DIN battery covers are found on BMWs and Mercs)."

With careful selection, the vent cover from the old Jaguar battery can be used on a generic replacement battery. Georges Krcmery says: "The EXIDE Mega-Cell # E42 50W has a rectangular slot around its filler caps which exactly matches the vent cover with only a slight adjustment: I had to cut off about 1 cm of the slot's lip to accommodate a similar widening under the nipple of the vent cover. It then snapped right into place. The battery is about 1/4" too wide to fit in the tray. Fortunately, the bottom of the battery has extra plastic on each side and it is possible to carefully saw off 1/8" on both sides to make it fit."

Michael Neal recommends a battery made by Optima. This is a lead-acid unit but uses six separate coils instead of plates; it uses a gel electrolyte and is sealed, no vent required. "So far they have proven nearly indestructible." It is about twice as expensive as normal batteries and comes with a 6-year warranty, free replacement within the first two years. Neal claims this battery will really last twice as long as normal batteries, so the actual cost of usage is comparable. "There is only one basic size, top post or combo post. Top will work fine..."

William Noorloos adds his experience with installing this battery: "...when I walked towards the trunk with the Optima in my hands it jumped the remaining 3 feet all by itself into position, and just sat there waiting to be connected! It's a total fit. 100% No fiddling. As a bonus the original Jag venting thing (Non-metallic British part and Lucas, but it has not broken yet) fits 100% over the Optima's 2 emergency pressure relief valves. So in the event of an alternator thinking it has to drive standard household appliances, and thereby blowing the battery, the (probably messy) inside of your expensive Optima will not end up in your trunk."

Whatever battery you use, you will want to reinstall the plastic cover over it. If you can make use of the original battery hold-down bracket, it may make life easier. With the Champion 78-2 described above, it would fit except that it blocks off the vents, and the tangs protruding downward on either end of the battery interfere with a built-in handle on the battery. Easy enough to cut the tangs off. The vents require a little more care, however; cutting enough of the bracket to clear the vents might render it two pieces! However, with judicious cutting, the top edge of the bracket can be notched all the way around the corner and part way down the side, leaving a portion of the side intact. If the height comes out too low it'd be a simple matter to put something under the battery to space the battery and bracket up enough to hold the plastic cover properly.

Alternative plan B is to forget the stock bracket and simply fashion a bar across the top of the battery. Longer J-bolts can be used, and two 1/4" holes made in the top of the original plastic cover. Then, after the battery is secured with nuts and washers, the cover can be installed and additional nuts -- real pretty cap nuts or threaded knobs, they show within the boot -- can be used to secure the plastic cover.

FYI: the battery compartment in the '83 XJ-S is 10 inches by 6-3/4 inches. The ideal battery height must be shorter than 8 inches, terminals included. The height to the flat top of the Champion 78-2 is 7 inches, and it fits with room to spare. It is highly recommended that you confirm the size of the compartment in your own car before shopping for a battery; the various documentation on what size battery to use, including those cute computerized battery selector displays, seem to be wrong more often than they're right.

One general observation about car batteries and warranties: There are some excellent $60 batteries out there with 60-month warranties (or longer). However, some $60/60-month batteries are actually a scheme to sell you a $40 battery of the same make every 3 or 4 years. If you buy a 60-month battery and it dies without due cause in far less time, you might be well advised to simply write off that warranty and buy another make -- unless, of course, you don't mind having to replace your battery every 3 or 4 years.

There are some people who select batteries on the basis of cranking amps. The logic works like this: The car only requires a certain number of cranking amps to start, and almost any battery will start the car when new. However, as the battery ages, its cranking capacity diminishes with time, until eventually the battery will no longer start the car. The more cranking amps the battery has to begin with, the more it can deteriorate before replacement is required. This theory assumes a lot, including that different batteries deteriorate at comparable rates and that the battery doesn't suffer other types of failure such as internal shorts. As such, this theory probably doesn't apply to unusual batteries such as the Optima, but may be a fairly valid method of comparing conventional batteries.

But to this theory must be added another monkey wrench: In order to maximize cranking amps, the plates within batteries must maximize surface area, which is done by making them look like grids or screens rather than plates. With successive charges and discharges, these grids get more and more deformed (metal is etched away when discharging, plated back on when recharging, possibly in a different place than it was before), possibly reducing the cranking capacity faster than flat plates would. Also, the grids might fracture more easily with vibrations, causing internal shorts.


DEAD BATTERY PROBLEMS: If your battery is dead after the car sits for a few days, it's time to check for current flow when everything is supposed to be shut off. Craig Waterman says, "On Monday mornings the battery would be flat. When I replaced the bulbs in the boot lights I did not think to check that the switch was closing and with a washer under each screw it is now turning off. So if your battery is going flat check that boot light switch." Of course, you normally have the trunk lid open when checking battery drain current and therefore have to have the boot lights disconnected by other means, so this particular possibility may be easily overlooked.


AVOIDING A DEAD BATTERY: Scott Jarvis suggests: "You can order a Battery Buddy from Outer Banks, (800) 682-2225, part # batbud. It mounts to the side of your battery and monitors the voltage. When the voltage drops below a set level, it automatically switches off to preserve the battery. You just reset a breaker and away you go! Many of the Boating catalogs should carry this and you may find a better price."

Kyle Chatman responds: "You can also try Priority Start from BLI International, Dept HR12, 17939 Chatsworth St., Ste. 521, Granada Hills, CA 91344, 800-780-8276. It monitors voltage drain when the switch is off and disconnects the battery if it gets too low."

Ned Blagojevic counters: "This is available in a kit form from Jaycar Electronics (Sydney), kit number KA-1739. The kit was published in Electronics Australia (Jan 92 issue). It connects to the accessory line and measures line voltage. If voltage drops to preselect limit between 10.9 and 11.9 it shuts off the flow. The kit includes a relay and specs."

John Setters provides a different alternative: "Here in NZ an enterprising company called PowerBeat has been formed to manufacture the answer to starting problems. They have developed an automotive battery which I believe is in two portions - one section runs the general electrics, the other is reserved exclusively for engine starting. The URL for PowerBeat is"

Sears also sells a battery with a switch on it, so you can switch to a "reserve" and get started.


ELECTRIC MOTOR LUBRICATION: Stefan Schulz and Chuck Johnson Jr. forwarded this procedure, originally from Chuck Johnson Sr., for oiling a "permanently lubricated" electric motor: "It is possible to lubricate a "permanently" lubricated bearing by oiling the wicking that surrounds the bearing. To do so take a sharp awl (punch) and with a hammer punch a hole into the ëbell' shaped cover over the bearing housing. Do this through the vent holes in the motor and not in the end of the motor itself. The wicking is housed on the inside of the motor in a ëbell' shaped tin cover so it is easy to poke a hole in it. Then just take an oil can (I use a PLEWS oiler so I can get some volume in there but almost any oil can that can put some pressure on the oil will work), and ëflood' the wicking. This way you do not have to take the motor apart to get the bearing soaking in oil. After this you can periodically lubricate the bearing by just re-flooding the wick through the hole you have made. This technique works with all motor types, auto as well as small appliance and large appliance motors."

The bearing cover that you are punching a hole in is very thin metal, much thinner than the housing of the motor itself. If you punch near the center, you may hit the bearing itself, and possibly damage or misalign it. Punch the hole near the outer edge of the cover; there will be nothing under there except the felt that's supposed to hold oil.

Of course, some motors don't have suitable vent openings, so you may have to open the motor anyway. This method still applies, though, since the bearing inside is almost always retained by a permanently-attached cover of this sort and oiling is almost impossible without punching a hole.

Another favorite item for applying the oil is a hypodermic syringe, preferably one with a fat needle. With a little luck, you can buy one in your area without being arrested for drug abuse.

Now that you have a procedure, you can oil motors periodically or you can wait until they seize up. Your choice. Do you really believe "permanently lubricated" means forever?

In the specific case of the XJ-S electric radiator fan motor, Schulz adds "the motor is of the "definitely no user serviceable parts inside, so do not open me" variety. Then again, you can open the thing by forcing the pry slots at the top and close it again be replacing the cover and punching down a bit more metal from the side. Look at one and you'll see what I mean." Of course, bending the metal back and forth regularly might result in needing a new motor sooner than not oiling it at all. In these cases, you might try a different idea: drill a hole through the housing itself, aiming for the same area adjacent to a bearing, and apply oil without disassembly. If it is important to keep water or dirt out of the motor, cover the hole with a piece of aluminum tape when you're done.


OIL PRESSURE SENDING UNIT: Many people confuse the two separate items on the XJ-S, both located at the top rear center of the engine, just below and behind the bellcrank. The smaller item is the warning light sender, and is a relatively cheap item. The larger part is the sender for the gauge, and it is more expensive and less likely to be available at a generic auto parts store.

The sending unit is a simple variable resistor. Jim Isbell says "I have opened up one from a series 3 XJ6 and found a mechanical diaphragm to wirewound pot contraption. It essentially acts as a variable resistor that shows high resistance at low pressure and low resistance at high pressure."

The gauge itself is actually a current-measuring device wherein the current heats a wire which expands to move the needle. In fact, all the gauges except the voltmeter are essentially the same. Because of the heating required to operate, such gauges always move slowly and calmly rather than zipping up and down and making drivers nervous.

Mike Cogswell reports that earlier Jaguar senders were different than the later -- and they shouldn't be mixed. "Turns out that the S2 E-Types (and probably XJ-6s of the same vintage) used 80 psi gauges while the V12s used 100 psi gauges. The gauges are identical except for the markings, but the senders are different since they are the same resistance at different pressures."


OIL PRESSURE GAUGE: Val Danilov reports, "Once I was sure that the oil gauge was faulty and not the sending unit, I pulled the gauge out of its housing by removing 3 screws from the back of the plate the gauge was attached to, as well as 2 metal clips. It's pretty much self-explanatory once you get to it. Once the gauge was out, in good lighting, you can see several hair-thin metal wires that run from the winding to 3 metal posts on the periphery of the gauge. The wires are soldered to the posts in such a way that they appear to be misplaced (as if they should extend farther to some other point), when in fact they are simply so small that you cannot easily see the points of attachment. When trying to move them with a tiny screwdriver, I found one wire which was loose. I used a regular soldering iron to affix the wire back on the post. Voila! Problem solved.

"When the gauge is out of the instrument cluster, it is very easy to test it with a 12 volt supply by simply connecting one of the electrodes to +, while grounding the other electrode. Note: the gauge has 3 electrodes (nuts on the threaded ends of the posts), do not use the middle post. The post nearest the bottom of the gauge is ground."


85 MPH SPEEDOMETER: Regarding why some XJ-S's came with 85 mph speedometers, Randy K. Wilson says, "It affected 80, 81 and 82. It may also have been in during 83... not sure." This author's '83 has a normal speedometer -- but perhaps it was retrofitted.

David Berman adds, "It resulted from a regulation from the US National Highway Transportation Safety Administration (NHTSA) during the leadership of "safety-czar" Joan Claybrook, during the regulation-happy Carter administration. The purpose was to prevent kids from being enticed by the "century" mark. It was effective for the 1980 model year.

"The regulation was thankfully scrapped in 1983 as part of a regulation-reduction program of the first Reagan administration. Most non-US vehicles returned to "real" speedometers for the 1984 model year, but US manufacturers retained the 85 mph speedos, at least for their high-volume car lines, for a very long time."

If you don't like the 85 mph speedometer, it can simply be replaced with a normal speedometer from a different year. John Napoli says, "I did this on my car about a year ago. Bought a 160 mph unit from a junkyard. Installed easily and works great." Of course, the replacement speedometer will likely have a different odometer reading, and you'll just have to deal with it.


Electric Windows


ELECTRIC WINDOWS: There are reportedly three different types of window motor used in the XJ-S coupe: A Delco unit up to 1987, a different Delco unit 1988-89, and a Bosch from 1990 on. The early Delco motor has a large cylindrical housing, while the 1988-89 Delco unit has a smaller, more rectangular housing -- perhaps better described as a cylinder with two flat sides.

The convertibles, of course, have another motor operating the rear windows, and apparently have different units in the doors as well.

Unfortunately, problems are reported with all types, even though none of them are Lucas. Some of the problems discussed below apply to all, and some apply only to particular units as noted.


ELECTRIC WINDOWS -- KEYLESS OPERATION: Some of us prefer the electric windows to be operable whenever we're in the car, not just when the ignition is on. If you share this preference, there is a "window lift relay" under the passenger's side of the dashboard that provides power to the windows whenever the ignition is on. All you have to do is remove this relay and connect the power wire directly to the wire to the windows, and the windows will operate whenever the buttons are pressed. Since the buttons are inside the car anyway, it's not exactly a security risk.


SLOW-MOVING WINDOWS: The early Delco windows always move slowly. This tip is from Leonard Berk: His windows operated very slowly, so he sprayed WD-40 down the frames without even dismantling the doors. The windows operate like new. Perhaps WD-40 isn't the ideal substance since the odor may be objectionable to some people, but it is worth noting that lubrication may be in order. Victor Naumann says, "Try not to use oil in the channel, it destroys the rubber. Silicone spray or graphite works OK. WD-40 is a great lube, but not for rubber, it makes it swell. Jag makes a very expensive lube called Glietmo, but I prefer silicone."

Paul Bachman says, "In my experience, lubricating rubber window guides is only a short term solution and seems to aggravate the sticking in the long run (gets gummy as it enevitably dries out). I have had very good success lubricating the guide rails on electric windows (including my 85 XJ-S) with graphite. It is difficult and a little messy to get it rubbed into the right places, but once in place it works for a long, long time."

On the author's car, one reason for slow windows was that the little roller that slides in the track at the bottom of the glass had gotten all screwed up -- see below.

John Himes talks "...about possible fixes to the drivers window not going all the way up without using their hand. On my 88 XJ-S, the problems was that one of the screws was removed by a PO, or had fallen out over time that mounts the window motor to the door & the others had become loose. The motor assy. would move when you raised or lowered the window. After tightening the screws & new lock washers (with the window all the way up so it would fit correctly), the window now goes all the way up & I no longer have the fingerprints on the window (inside anyway)."

John Setters reports: "Two problems caused my drivers side window not to close fully without assistance:

  1. Window motor mounting had come loose.
  2. The lift assist coil spring was binding on itself.

"Firstly remove the door trim panel - the hardest part! I found that I needed to close the window fully before tightening the motor mounting bolts. This is the way to assure correct positioning of the closed window. Do this by applying upward lift with your hand under the slide rail at the lower edge of the glass. Then tighten the bolts.

"Complete lift was hampered by lack of spring tension. Although well lubricated by grease too much friction existed. I applied spray CRC to the spring then operated the up and down movement to work the CRC into the spring coils. Heh presto it all works fine now."

John Napoli suggests adjusting the track at the rear of the window. There are two screws that hold this section of channel in place; one is under the door panel near the bottom rear of the door, and the other is clearly visible on the end of the door above the latch. The track is removable to facilitate replacing the glass. The bottom screw has a very large washer on it and fits through a large hole in the door sheet metal, so the track can be moved around quite a bit before tightening it down. The upper screw doesn't have as much room to move, but can still move a little. It is helpful to loosen both screws at the same time to fully investigate the range of possibilities.

Napoli also suggests "If you can't find an adjustment that solves the problem, replace the lining of the rear channel. Jag sells a replacement channel. I suspect that good old aftermarket channel felt can be installed in the old channel assembly." The problem with old channel felt is that the fur wears off, allowing the glass to rub directly on the rubber underneath. The friction is hence much higher than it should be.

If you have the early Delco window motors, once you have addressed all the possible problems listed above, your windows will still move slowly. The final solution is to install a relay control system; see below.


WINDOW/TRACK SEPARATION: John Napoli says: "I once had a weird window failure in my car. The PO had replaced the rear window channel on the drivers side. One day I lowered the window and thunk -- the window drops down out of sight. Opened the door up and found that the metal channel that the glass rides in had been pulled away from the glass. It was as if the glass had a positive stop on the way down. The motor kept on pulling the glass down after it hit the stop and pulled the arm off. Put it back together and it soon happened again. I solved the problem by taking the glass out, supergluing the arm to the glass (in the correct location!) and installing a sophisticated support that the steel arm would hit when the window was lowered. It was a carefully shaped chunk of 2x4. You need to glue the channel to the glass in addition to adding the stop because if the channel is loose on the glass it will eventually slide sideways and prevent the window from opening or closing properly. The glue locks the channel in position and the stop prevents the window from dropping too far and allowing the motor to pull the channel away from the glass.


ELECTRIC WINDOW REGULATOR DRIVE ROLLER PROBLEMS: The little roller on the end of the motor arm on one window in the author's '83 XJ-S was FUBAR. Basically, the shaft the roller turns on is attached to the arm like a rivet, and this attachment worked loose, allowing the roller to cock sideways and jam in the track on the window. As the motor forced it back and forth in the track, the edges of the sheet metal track chewed the plastic roller all to bits. No, you can't buy a new roller from Jaguar -- they want you to buy the entire window regulator mechanism. The ë83 clearly has the early Delco regulator, but all of the regulators have rollers of some type and may occasionally have similar problems.

For anyone with a lathe and some plastic stock, it would be a simple matter to make a new roller. Unfortunately, I don't have either. I went to a building supply store and looked through their collection of rollers intended for sliding closet doors, drawers, shower doors, etc. I immediately noted two concerns: 1) the roller in the Jag window was smaller than any of these; and 2) the roller in the Jag window has a sort of offset -- the bearing surface isn't in the center of the roller, but over to one side. In the Jag, the pin is shaped like the head of a flush head bolt, so that no part of the pin extends beyond the roller and jams into the track. Only a select few of the rollers in the building supply store had a similar feature.

I selected a package of "Closet Door Hardware" described as "No. 8544, 7/16" Offset Hanger Pr." and made by Door Products Inc.; I'm sure there are generic equivalents in just about any such store. This package contains two hangers intended for the top of a hanging, sliding closet door, each with a little roller to fit into a track. The 7/16" refers to how much the offset is, no importance here. In fact, the entire hanger is forfeit except for the roller itself. There are probably several other types of hangers, with various offsets, all using the same or similar roller. It is necessary to grind off a rivet flare to remove the roller from the hanger.

The roller acquired is the smallest I found, but still too large; it is about 20mm in diameter, while the Jaguar window roller is about 17mm. However, it was a simple matter to mount the new roller onto a 1/4" bolt, chuck it up in a drill, and grind off the outside edge until it was the correct diameter. This roller, along with the Jaguar original, is illustrated in Figure 15.

This roller also had the offset bearing, although it was not as long as the Jag original. When assembling, it was necessary to add a few washers behind it to space it out the same distance from the arm as the original had been. I made washers out of plastic so they wouldn't jingle. I also made sure their OD was small enough to not interfere with the window track. 

I also was able to find a shoulder bolt, or "axle" bolt, that I was able to modify for use. It was an Allen socket head bolt with a 1/4" diameter shoulder 3/8" long, and a 10-24 threaded end beyond that. If I had intended to use this bolt to hold the original Jaguar roller, I would have had to grind a taper on the bottom side of the head to match the tapered surface within the roller and allow the head to recess far enough into the roller so as not to protrude at all.

For this new roller, however, the problem was different. The new roller has a recessed opening for the head of the original pin that held it, but it's flat-bottomed, not tapered. There is therefore no reason to grind on the bottom side of the head, but the top side protrudes entirely too far -- this head is much taller than the recess is deep. So I had to grind about half of the height of the head off. This removed the entire Allen socket, leaving me no way to tighten it. So I cut a straight slot across the top for use with a screwdriver.

When assembling, I put the roller and the homemade plastic washers on this shoulder bolt, screwed on a nut, inserted it through the hole in the arm, and put another nut on the back side to hold it. When tightened up, this positioned the roller about the same distance from the surface of the arm that the original had been.

I chose not to install this roller in the original hole in the regulator arm. Instead, I drilled a new hole 1" closer to the motor itself, making the arm effectively 1" shorter, in hopes of improving the leverage the motor has moving the window. This worked perfectly, but since the arm is 15" long to begin with, this provides only a small percentage improvement in leverage. Still, it's easy to do, and every little bit helps.

Of course, the window motor and regulator assembly is an AC Delco; perhaps you can figure out what other cars it was used in and find a cheap replacement in the local junkyard.


ELECTRIC WINDOW SWITCH PROBLEMS: Reports of problems are more common with earlier Delco units. That may be partially because the cars are older, but the early Delco system definitely suffers from overloaded switches. The switches are inadequate for the current involved and the contacts get burned. Even though the later Delco and Bosch motors are physically smaller, they still move the windows at a good clip and probably draw a comparable amount of current; we'll probably hear more about switch problems in later cars as the years go by.

Bob Colson of the Jaguar Club of Southern Arizona points out that the window lift switches can be taken apart. First, remove them from the panel -- easiest to do by first removing the panel so you can push them out from behind. Then, by spreading the housing slightly, the rocker itself can be popped out. Then the parts can be cleaned up and repaired as needed. The two rocking contact plates are symmetrical but only one end of each gets worn, so the plates can be reversed to extend their life. The cruise control on/off/resume switch is constructed similarly.

Phil Patton adds: "Usually it seems the plastic things on the ends of the springs wear unevenly for some reason. When cleaning the switch replace the one from the left side to the right and vis-a-vis."

Another solution is to replace the switches with generic double pole/double throw self-centering rocker switches with better contact ratings. The difficulty here, obviously, is getting them to look right. Phil Patton sends this tip: "I have found a switch which is less expensive, IMHO looks much better, and I am positive will last much, much longer. This part fits the existing hole perfectly and has a small, coloured illuminated strip across it, making it easy to find in the dark. It is rated at 20 amps @ 12 volts and is (unlike the Jag switch) completely sealed so that dirt cannot contaminate the contacts. The part is GC number 35-3565 (green light) or 35-3570 (red light). They should be available from any decent size electronics parts house. The only modification necessary to use this part is to cut off the plug on the wiring harness and replace it with push-on lugs on each wire. If you don't like the light then just don't connect it."

Stephen Wood says, "I replaced the power window and power lock switches in my '76 XJ-S with '82-92 Camaro/Firebird units, $10 ea. new and they work great. I had to make a wiring jumper and a sub plate for mounting, but they function better than the Jag ones ever did."

Perhaps the best solution, and one that maintains the original appearance, is to install relays to operate the windows and operate the relays with the stock rocker switch. See below.


WINDOW CONTROL RELAY INSTALLATION: Both the dragging window motors and the burned switch contacts are symptoms of the same problem: There is too much current going through those switches. The high resistance, due to marginal or overloaded contacts, results in less than ideal power to the motor and causes the contacts themselves to fail often. This author measured the voltage at the window motor with the window trying to close, and it was less than 8 volts -- and dropping below 7 volts as the motor struggled. This operating voltage means the motor is only developing about 45% as much power as it would at 12V.

A set of window control relays will provide full battery voltage to the window motors, eliminating the losses in the wiring harnesses and switches. See Figure 16. Two SPDT relays will be needed for each window, an "up" relay and a "down" relay, and each will need to have serious contacts -- at least 10-amp rating. Since the current needed to operate the relays is minimal, the rocker switches should last forever -- even if they've already been abused and cleaned up a couple times.

The XJ-S comes with a relay referred to in the Jaguar literature as a "window lift relay"; all this relay does is turn off power to the windows when the ignition is off. I will continue to use that term when referring to that relay, and will call the new relays being added in the following scheme "window control relays." Try not to get confused.

Since window motors are permanent magnet motors, the direction they run depends on the direction of current flow. The wiring within the motor itself is not grounded. To run one direction, the switch grounds one motor lead and applies 12V to the other. To run the other direction, the same switch grounds the second lead and applies 12V to the first. The window control relays should be wired to do the exact same thing. In the wiring scheme shown, the normally-closed contacts on the relays ground both leads of the motor when the relays are idle, and each relay switches one lead to 12V power when energized.

A massive power wire -- 12 gauge or so -- must be routed to the window control relays directly from some heavy-duty source (any big, fat brown wire). You can toss in an inline fuse for safety, but it's probably a better idea to use the original thermal circuit breaker; it will do a better job of protecting the motor from overheating if the power is left on (somebody sets a book on the switch).

For the passenger's side window, it is quite convenient to use the existing 12V power source and circuit breaker for the windows, leaving the breaker mounted right where it is; just connect a new wire with a 1/4" spade terminal to the output side of the breaker and route it to the new relays.

For the driver's side, it may be preferable to just buy a new circuit breaker and power it from a lead to the fusebox; this would eliminate the necessity to run a heavy wire from the existing breaker on the passenger's side across the car to the driver's side. The original "Otter" circuit breakers are inordinately expensive and of unknown rating (apparently big enough to allow both windows to run at once, probably too big to properly protect a single window motor), but generic circuit breakers are available in auto parts stores in 10A, 15A, 20A, 25A and 30A ratings for around $5 each. The 10A should work for one window motor; if it trips too often when the motor seems to be operating properly, just replace it with the next larger breaker. All of these generic automotive circuit breakers are "thermal" type, as opposed to the electromechanical circuit breakers typically used in homes.

For the relays, 12V DPDT relays with 15-amp contacts from Radio Shack, cat. no. 275-218, will serve nicely. Since SPDT relays will do the job, wire both contacts together; two 15-amp contacts working together definitely should handle this job!

The sockets that Radio Shack sells for these relays are not recommended; buy a handful of 3/16" spade terminals instead. Radio Shack seems to only offer 3/16" spade terminals in a box with a lot of other connectors, and since you need 16 of them you'll be buying a lot of boxes. If you go to an auto parts store, though, you may be able to buy a box with the correct "crimp-on" terminals alone. Even if the terminals come with plastic insulating collars, it is suggested you rip the plastic collars off and throw them away, solder the wires to the terminal after crimping, and insulate them with 3/16" and 1/8" heat-shrink tubing.

Since SPDT relays will work, automotive relays are another option -- if you can find some with an 87a (NC) terminal. Most of the relays sold in auto parts stores (usually for controlling driving lights) have two 87 (NO) terminals and no NC terminal, which won't work. Suitable relays include the one used on the XJ-S electric radiator fan, SRB411, and all of its substitutes.

Another option would be to use two normal driving light relays (no NC contacts) instead of each SPDC relay. Rocking the button should operate both relays, and one should make the power connection while the other makes the ground. This wouldn't make any sense if relays were priced the way they should be, but the fact is that you might find two driving light relays are cheaper and/or easier to find than one SPDT relay.

Automotive relays require 1/4" spade terminals, which are a good deal easier to find than the 3/16" terminals needed for the Radio Shack relays. Again, insulate them with heat-shrink tubing, 1/4" and 1/8" this time.

The relays can be located anywhere between the switch and the motor; simply break into the RG and GR (right side) or RU and GU (left side) wires from the rocker switch to the motor and wire in the relays as shown. Within the door itself is one possible location; in this case, a massive ground wire should be routed back into the car -- relying on ground contact through a door hinge is not recommended. Also, before closing the door up, it'd be a good idea to fasten the relays down (possibly with foam tape) and tie the wires down, and run the window up and down and operate all the latches to make sure the wires aren't in the way of moving parts.

Another possible location is adjacent to the footwells; you can intercept the wiring near the door hinge by removing the kick panel on the side of the footwell just forward of the door (2 screws). There is a pocket that looks like it was made for these relays behind the kick panel. There is a door lock relay in the same space, but it isn't taking up all the room. The wires from the door all go through this space, and there are a lot of them -- stereo speaker, electric mirrors, puddle light, door lock, and window. They are also plenty long enough, making it a simple matter to cut into the two window wires and install the relays. This location makes it unnecessary to have to route heavy 12V and ground wires into the door, or even to take the door panel off.

The relays can also go within the console if preferred, although that reuses a lot of the original wiring to the motors and reduces the potential benefits of installing really heavy power wiring.

It doesn't make good electrical sense to use the existing circuit breaker to protect the wiring to the rocker switches and new relays, since that's a heavy duty breaker and they are now a low-power circuit. Instead, provide an in-line fuse to the rocker switches; a 2A or 3A fuse should be plenty to power the relays. Physically, this means that the NU line from the window lift relay to the rocker switches is disconnected from the relay and connected to a fuse instead. You can use a generic fuse holder for a professional installation, or you can simply put 3/16" spade terminals on the wires and connect them directly to one of those newfangled plastic fuses.

Remove and discard the window lift relay, it won't be needed any more; the window control relays themselves will accomplish its task. Unfortunately, the window lift relay doesn't have a NC connection, so it cannot be reused as one of the four window control relays.

Where the power to the other side of the fuse comes from is a matter of preference. If you wish the system to work the way it originally did (windows won't move unless the ignition is on), then connect the WK wire that originally controlled the window lift relay to the fuse, as shown in Figure 16. If, on the other hand, you'd rather the windows worked whenever you hit a button regardless of ignition, just connect the fuse to a constant 12V power supply -- and there happens to be one right nearby, connected to the input side of the circuit breaker.

A minor complication: One might assume that the window rocker switches are a center-off, DPDT operation, and the wiring diagram for the window circuits in the Supplement to the Jaguar XJ-S Repair Operation Manual is obtuse enough to let you go on thinking that -- but they are not. Each rocker switch is actually two individual SPDT switches, neither of which is center-off; both have NC and NO contacts. With the rocker in the center position, the NC contacts on both switches happen to be connected in such a way as to send 12V to both leads to the motor. Since 12V at both leads results in no current flow, the motor doesn't move. When you rock the switch, one of the two internal switches disconnects the 12V source and connects that motor lead to ground, while the other internal switch doesn't move -- hence, the motor runs. Figure 16 shows the switch schematically correctly, although it doesn't really indicate the actual physical operation properly.

All of this is normally just fine, except that all those leads are hot all the time. Something to keep in mind while working in the area, especially if you have bypassed the window lift relay so the windows are operational at all times with or without ignition.

With the window control relay installation, however, these hot leads cause the relays to be energized when the windows are not moving. Rocking the switch causes one relay to unenergize, and the system will in fact work just fine; the relays will just get warm. However, if you have wired the system so that the windows can be run with or without ignition (see above), the relay coils would be draining the battery when the car is parked. Ungood.

The solution is to exchange the 12V and ground connections to the rocker switch so that both motor leads are connected to ground when the rocker is centered -- just like you'd have expected Jaguar to do in the first place. You can make this change by cutting and splicing wires, but an easier way is to move the connectors around on the plug that connects to the bottom of the rocker switch, putting the NU wires back where the B wires were and vice versa. With a piece of 3/16" OD brass tubing (available at hobby shops), it is a simple matter to pop the connectors out of the plug; just insert the tubing into the round hole around each connector, and it will compress the tangs on the sides of the connector itself and allow the connector to be pulled out the back side. Then they can merely be pushed back into the proper holes until they snap into place. This change may even be desirable without installing window control relays, since the windows will still run exactly the same way; you just won't have hot leads when working on the car any more. Note that, for operating window control relays, the ground wires could merely be removed since they are not used.

When fiddling with all this wiring, rewiring, relay installation, etc., etc., trying to keep track of which circuit will move the window up versus which one will move the window down will drive you nuts. Instead, just forget about it. When you're all done and everything is working fine, if the button must be rocked the wrong way to move the windows, just turn the connector around on the bottom of the rocker switch. If you prefer, you can reassemble the console but leave the rocker switches hanging out of it by the wires; when you're ready to test it, just hold one rocker switch in your hand and push it one way or the other and note which way the window moves. Then turn the switch whichever way is correct and snap it into the panel.

This author has installed window control relays in my '83 XJ-S. I can report that the modification is a resounding success; the windows now zip up and down like they should. It is now clear to me that this is yet another modification that should be done by all XJ-S owners ASAP, before their stock window switches bite the dust from overload.


ELECTRIC WINDOWS -- EARLY CIRCUITRY: According to the Jag manual, "Selections can be made on one switch at a time, the driver's switch over-riding the other panel switch", possibly to avoid overloading the circuit breaker. However, the supplement shows no such override and both windows on this author's '83 run at the same time. Randy Wilson says, "The SII XJ6, and early XJ-S, were set up in the manner your book describes. The switches are double pole, triple throw (down, pass-through, up). With this early system, you could only run one window at a time. And, if a switch failed such that the pass-through didn't work, all windows downstream also quit. Since the most used window, the L/F, is also first in the daisy-chain, it's not uncommon to see a SII with no working windows. This went away (all switches wired in parallel) with the SIII. I'm not sure exactly when the S changed over, but it was certainly by the time the H.E. was introduced."

If you have an early car and are having trouble with this system or these switches, the ideal solution might be to simply install the window control relay scheme described above and delete that daisy-chain nonsense. If your original switches can be made to work at all, they can be wired to operate the relays, and you will no longer be limited to one window at a time. Since you would be providing new and substantial power wiring to the window motors, there's no risk of overloading any existing wiring.


1988-89 ELECTRIC WINDOW MOTOR FAILURES: On the ë88-89 Delco units, the housing on the motor itself gets loose and jams the rotor, or lets water in. Victor Naumann says, "I have replaced a lot of motors that the back has fallen off of and water has ruined."

Steven Draper reports, "After taking the door apart, I noticed that the case on top of the window motor that holds the magnets is held on by only two bolts. The rear bolt had slipped some, and could not be tightened completely because of the soft metal. The bit of play between that casing with the magnets and the internals of the motor that spin about was enough to cause the motor to only work when you beat the side of the door. I inserted a slightly larger bolt with a nut on the bottom. I was able to put the new bolt in without taking the motor out. Believe it or not, the window now rockets up and down. If you've got a window that doesn't want to go up and down and tapping on the door helps, this could be your problem.

"It was interesting because the case had four bolt holes but the motor part with all the gears in it only had two holes for the case to attach to." It might not be a bad idea to put some aluminum tape over the unused holes to keep water out.

Peter Cohen provides part numbers: "The January 1987 - January 1989 parts book lists the non-convertible window motors as: Left: JLM975, Right: JLM974, and the regulators as Left: BCC5775 and Right: BCC5774. Convertible is listed as Motor: Left: JLM1496, Right: JLM1495, with the convertible regulator listed as Left: BDC5079, Right: BDC5079.

"The right side Delco motor that I removed had a paper label with the number 20060098 above the numbers 121 and 30P8 (the left side label was illegible).

"BTW, on the Delco motor, if you put the stator on reversed from how you took it off, the motor does the opposite of what the switch intends." Might be a good idea to mark which way the case goes before disassembly, although you could conceivably just turn the switch around in the console.


1988-89 ELECTRIC WINDOW MOTOR SOLUTION: Peter Cohen reports, "'88's & '89's are known to have problems with the window motors. I have an '89 XJ-S and have replaced both window motors with the new style Bosch motors. I highly recommend them. The windows just zip up and down like they never did with the Delco motors. If you have an extended warranty, this should be a no brainer -- make them buy you the new motors. If the warranty company won't come through, sue their no good ass in small claims court.

"Some other insights into the window motor upgrade:

"1. When this upgrade first came out, it was only sold as a complete motor/regulator assembly. It is now available as two separate parts.

"2. When I bought my left side assembly from SICP a few years ago (about $325 then), two of the holes on the motor seemed not to line up with the holes in the black sheet metal panel in the door, & I had to drill new ones. This was not a problem with the right side, separate motor & regulator assembly which I bought in April from SICP on their close outs, but I did have another problem: Both the regulator and motor that SICP shipped me as right side were actually left side. The regulator assembly was in a sealed Jaguar package with the correct Jaguar part number for the right side. I took this to the local Jaguar dealer who cheerfully swapped it for a left side regulator, without my asking, and without asking where I got it. Being so successful with the regulator, I took the motor to another Jag dealer. Now, here's where it gets interesting. The motor from SIPC came in a Bosch box, so I was a little nervous about trying to swap it at a dealer. I brought in the motor without the box, and again, the dealer swapped it without my asking. However, the number on the motor was different enough from the one I brought in that it wasn't just the difference between left and right. Also, the motor from Jaguar comes with 3 torx screws, and while the Bosch unit had no external wiring at all (just tabs to connect the wires), the Jaguar issue not only has the wires, but they are potted onto the motor. This leads me to believe that there is a standard issue Bosch motor that we can buy and adapt, even if Bosch won't sell the Jaguar number.

"3. There is a different type of plug on the Bosch motor (although still only 2 wire). You can cut & splice your old wires, or Jaguar sells a clean little adapter assembly to do it right. I have done it both ways, and both work. The adapter is $40, so you really have to want it."

"I get the impression that SICP is no longer selling window motors because of the problems they have had.

"A few weeks ago, I found myself in a Mercedes repair shop, and noticed a window motor lying on the table. Dang if it didn't look exactly like the one I put in my XJ-S. Which leads me to speculate: How many other cars use the same motor? Audi? BMW? Volvo? Saab? Opel? A wrecking yard Bosch motor in conjunction with a new Jaguar window regulator may be just the ticket for replacing those crappy Delco motors without bleeding from the ears at Jaguar's price."

"The Bosch motor's drive gear has a different number of teeth, so the regulator gear of the Delco won't mate with it, thus the need to replace the regulator."


BOSCH ELECTRIC WINDOW GEAR FAILURES: On the 1990-on Bosch units, the gears strip. Matthias Fouquet-Lapar says, "I almost fall flat on my face when the workshop told me that the window motor for a '91 XJ-S was more than $800! They found a way to adapt the older motor type. They told me that there is some nylon drive gear which easily breaks and there is no good fix available, so they retrofitted the older type motor. It seems to require some major rework to the window mechanism though." Considering all the expense Peter Cohen went to in upgrading his Delco motors to the later Bosch (see above), he probably doesn't want to hear that shops are doing the reverse.


ELECTRIC WINDOWS -- CONVERTIBLE: Larry Barnes says, "I just got to repair the left rear window motor on "her" '92 Convertible. I also had this same problem with the right rear window motor. Dare I say it, "a design flaw"??? No, couldn't be...

"Seems in the gear box (the flat lid pops off for easy access) there is a ring gear and a worm gear and a output linkage linked to the ring gear with a 1/4" flat/round rubber pad/shock absorber. Well, there are three little "ears" on the rubber shock absorber that will break off and, get caught in, and jam up the works (always with the window in the down position when you are 40 miles from home and it's pouring down rain). They seem to have no other practical use!

"The fix is: Remove the FOD, spin around 3 times anti-clock wise, and reassemble. Everything works great again..."


ELECTRIC REAR WINDOWS (CONVERTIBLE): Trish Duffy says, "On the convertible, the two back windows automatically retract when the hood/top is lowered, and close when the hood/top is raised. These back window motors can burn out if the top raise/lower switch is held "on" for too long."

Larry Barnes says, "My 1992 convertible has a "Delco of England" window motor for the Rear\Side windows. I tried to order just the motor, but Jaguar wanted to sell me the whole shooting match (with regulator) for $360. I found a local motor shop the would rebuild the motor."

There apparently are other problems with these windows, though. Andrew Corkan says, "I have a '91 XJ-S convertible and the rear window, lowered automatically when the hood (convertible top) is lowered, stopped working. The window remained up, but otherwise the operation of the hood was not affected. I tested the usual, relay and fuse, etc...

"Following the Jaguar service manual, 1974-88, vol 4 page 76-11, I removed the rear quarter trim panel. I then removed the plastic motor cover. It is held in place by both adhesive and three plastic button fasteners. I missed one fastener and broke the thin plastic cover. I also unplugged the two motor wires.

"The failure was in the gearbox on the motor. The gearbox has a thin metal plate that covers a worm gear on the motor coupled to a plastic gear that couples to the window movement linkage. I removed the four bolts that hold the window linkage to the body. I lowered the window half way by hand and rotated the linkage to remove it from the recess in the body. ( I did not remove the rear storage compartment or the hood lift linkage as stated in the service manual. )

"I don't know why the gearbox failed. The gear box contains a rubber coupling consisting of 6 pie-wedge shaped sections that couple a three-pronged part on the plastic gear with a three pronged part on the metal shaft that runs out the back of the gear box. These wedges had popped out and knocked off the gearbox cover. It appears that the window motor is just run for a fixed amount of time and there is no switch to stop it, so maybe the rubber parts were just squeezed out when the motor stalled at the end of the travel. I saw no limit switches.

"I jammed the rubber back in place and replaced the metal cover and peened that back into place. When reinstalling the motor it is important to run the hood up or down so that the other window is in the halfway position (as per the service manual). This puts the window linkage in a position that allows access to all three mounting bolts for the gearbox. I repacked the gear box with general purpose grease, and added lithium grease to the linkages.

"It worked fine 6 times (up or down) last weekend. So far so good.

"The critical and possibly breakable part appears to be the plastic gear in the gearbox. All other parts are robust metal or easily cut rubber. If you find these gear boxes, keep the parts.

"The motor looked generic. If it fails it should not be too tough to find a substitute, just be sure you save the worm gear that is on the shaft.

"My time was 3.5 hours, mostly trying to figure out which screws to remove and how to remove the linkage. Next time it will take about 1 hour."


ELECTRIC REAR WINDOWS (CONVERTIBLE) -- ACCESS NEXT TIME: Julian Mullaney says, "I was buggering about with my XJS Convertible rear windows which wouldn't work properly (just like everyone else's) and noticed that the panel that covers the motors is held in by several screws, one of which is behind the window glass. If the window ever gets stuck in the up position, or any position except all the way down, this screw would be utterly inaccessible, i.e. behind the glass. This means that the interior leather panel could not be removed and the motors could not be accessed at all. One would be truly screwed if this were to happen. I think I will leave these screws out next time. There are enough other screws holding the panel in place."

Andrew Corkan responds, "It happened to me. I went to my basement and found a philips screwdriver tip, the kind you buy in packs of 6 for driving drywall screws with your electric drill. I then went to my local Service Star store and bought a strip of steel, 1/2 inch wide and 1/8 inch thick. I cut the philips part off the driver and drilled a hole in the strip of metal and brazed in the stub of the philips screwdriver into the hole. This gave me a right angle screwdriver, with a bend able handle, that was flat enough to get into the space. I could rotate the screw 90 degrees at a time and it took 15 minutes to get it out! If you do this be sure to file all the sharp edges off the metal; I then wrapped the metal in plastic tape to prevent damage to the leather. Before I replaced the screw I cut it off so it will only take two rotations to get out of the hole. Now that I think about it, maybe I will replace it with a hex head screw, easier to turn."


Electric Mirrors


ELECTRIC MIRROR DISASSEMBLY: Sorry to say, the electric mirrors were never intended to come apart. Here's how they went together: The plastic rim was put into place, then the motor assembly was put in over it, and then three screws were put in through holes in the mirror platform to hold all that to the housing. Lastly, the glass itself was mounted on the platform with foam tape -- completely covering the access holes to the three screws. Your chances of getting the glass to peel off of the plastic platform without breaking it are slim. Of course, if the entire reason you're reading this paragraph is because your glass is broken and you wanna know how to replace it, that's the trick -- just bust the glass into lots of little pieces until you can poke holes in the foam tape to get to the mounting screws.

If you don't wanna break the glass, you have a bit of a task ahead. Fortunately, you can easily see just how difficult it is before you even start. Run the electric mirror to the full up position, and pry it upwards a little more with a screwdriver and look under it. You will see two Phillips head screws. These two are not that difficult to get to. Run the mirror to full down and look between the top and the edge of the housing, and you should see the third Phillips screw dead center. This one's a real pain, since it's farther away from the edge than the lower two. Trust me, getting these three screws out and back in is the only difficulty with removing the motor assembly; if you can figure out how to do that, the rest is cake. The mounting lugs on the motor assembly are open slots, so removing the two bottom screws and just loosening the upper one may work.

As long as you have the thing out, a couple of suggestions: First, the plastic rim may have flashing tabs around the edge of the inner rectangular opening, notably at the 3 o'clock and 9 o'clock positions. These tabs may interfere with operation of the mirror, and should be cut off. In fact, it isn't a bad idea to use a sharp blade to cut about 1/8" off the right side of this opening, enlarging the entire rectangle.

Second, the motor assembly mounts with three lugs, but there is a fourth unused lug that gets in the way during assembly. You may want to just cut this fourth lug off to ease reassembly. It does nothing for operation, though, so you also might just leave it alone.

Third, the bottom center portion of the plastic rim distorts, so the screws tend to pinch the mounting slots right on the edge rather than getting a secure grip. My solution for this was to attach a 1" length of popsicle stick to the bottom center of the housing with a piece of aluminum tape. This holds the plastic rim up into the proper position while the bottom two screws are tightened.

Note that the motor assembly itself is also permanently assembled, by melting tabs. You'll have to grind them off to get it open, and then contrive some other method to hold it shut again.

The motor assemblies for the left and right sides are exactly the same, not mirror images or anything.


ELECTRIC MIRROR ADJUSTMENT SWITCHES: When the parts man at a Jag dealer was asked about these joystick switches, he had the part number memorized! We're talking junk here, and they charge $85 each for the two of them. Note that for '92 the joysticks were replaced by a fancy electronic adjustment scheme, and the following ideas do not apply.

Note: The mirror circuits are always hot, even with the ignition off. 12VDC won't electrocute you but it may cause burns or blow a fuse, so you may want to remove the appropriate fuse or disconnect the battery before working in this area.

Glenn Waterfield sends a description of how to rebuild the joysticks: "I was able to very carefully remove the pins holding the body of the switch together and strip down the pieces and clean the corrosion off them. To re-assemble the switch I did not want to try to reuse the metal pins that originally held it together since I will probably have to clean them again, so I found a tap just barely larger than the pin hole, a 4-40 I think, and carefully tapped the hole and put in three 4-40 nylon machine screws. If you try this I would recommend a clear work area with no carpet to drop the unbelievably tiny bits and pieces into."

If you'd rather just get rid of the junk switches, the following is a replacement scheme.

1. Make a flat rectangular panel to replace the original chrome escutcheon (see Figure 17). You can make this out of anything you think would look good in your car -- chrome-plated steel, sturdy plastic, sheet metal covered with leather, elm burl, etc.

2. Go to an electronics supply store and buy four toggle switches. They need to be "mini" or "submini" ("micromini" will also work if you find any, but you need to drill smaller holes in the panel), "DPDT momentary center off". This means that they not only need to have three positions, but need to return to the center position by themselves when released. The current here is very low, a 3-amp rating will do. Once you find such switches, they should be only about five bucks each. Technically, a DPDT momentary center off rocker switch would also work -- if you can find one small enough to fit four of them in the car.

3. You may also want to buy some Molex connectors, such as Radio Shack catalog no. 274-236 and 274-226, to replace the hokey originals.

4. Mount the switches on your panel. The upper two should be mounted vertically and the lower two horizontally, since there will be one up/down switch and one left/right switch for each mirror.

5. A soldering iron or gun is required here. Connect wiring as shown in Figure 18. Note that each wire connects to two terminals.

It is also possible to use only two DPDT momentary center off switches instead of four by adding a DPDT switch (non-momentary) to switch from left mirror to right. With this selector switch, a center off position provides a "lock" so the mirrors cannot accidentally be moved; while not strictly necessary, it wouldn't cost anything, either type switch is readily available.

Glen E. MacDonald went this route. "Not wishing to junk the chrome escutcheon, I used the three switch alternative, ie. two of RS 275-637 (one each for vertical and horizontal adjustment) and one of RS 275-626 (to switch between left & righthand mirrors). I found that the former switches could be very tidily mounted where the original joysticks were (in the escutcheon) by utilizing suitable diameter caps from magic markers, pared for length and drilled to accept the switch. The mirror selection switch is small enough to mount unobtusively in the leading edge (front portion) of the escutcheon. It works like a charm and, in my opinion, looks quite professional!" Figure 19 is based on MacDonald's input for wiring these switches. MacDonald cut the connectors off the original switches, and therefore the illustration shows the connectors and the wire colors from the original switches as well as the harness wire colors -- note that some mirror joysticks may have P wires instead of R.

Note: the author's local Radio Shack claims they no longer offer the 275-637 momentary switches nor any acceptable substitutes, but similar switches are available at most other electronics supply houses. A suitable switch is made by GC, part number 35-018.

It may also be possible to utilize the mirror switches from some other car. More and more cars use electric mirrors these days.

Once your mirror control switches are operational -- original or replacement -- it would be a good idea to wrap some plastic around the assembly before installing to keep rain that gets past the window seal from getting into the switches and corroding the contacts.



The Electrical System continues


Please help support the move to the new site, and DONATE what you can.
A big Thank You to those who have donated already!



Go to our Homepage
Improve your Jag-lovers experience with the Mozilla FireFox Browser!

  View the latest posts from our Forums via an RSS Feed!

Jag-loversTM Ltd / JagWEBTM 1993 - 2019
All rights reserved. Jag-lovers is supported by JagWEBTM
For Terms of Use and General Rules see our Disclaimer
Use of the Jag-lovers logo or trademark name on sites other than Jag-lovers itself in a manner implying endorsement of commercial activities whatsoever is prohibited. Sections of this Web Site may publish members and visitors comments, opinion and photographs/images - Jag-lovers Ltd does not assume or have any responsibility or any liability for members comments or opinions, nor does it claim ownership or copyright of any material that belongs to the original poster including images. The word 'Jaguar' and the leaping cat device, whether used separately or in combination, are registered trademarks and are the property of Jaguar Cars, England. Some images may also be Jaguar Cars. Mirroring or downloading of this site or the publication of material or any extracts therefrom in original or altered form from these pages onto other sites (including reproduction by any other Jaguar enthusiast sites) without express permission violates Jag-lovers Ltd copyright and is prohibited
Go to our Homepage
Your Browser is: CCBot/2.0 (, IP Address logged as on 14th Dec 2019 11:15:51