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XJ-S Electrical

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XJ-S Electrical

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.

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 "Vgroove" 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 $0.70 per 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 cause.

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 connector. If the crimp connector is the uninsulated variety, it may be possible to combine methods; crimp the connector to the wires, and then apply solder.

Crimp connectors can be purchased in automotive stores, often in a package along with other types of crimp-on terminals. Some of the terminals 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 metal 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.

The best insulation method to use is heat-shrink tubing. Heat-shrink tubing is available at some auto 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.

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 also works well on many terminals. If you select tubing barely large enough to fit over a female spade terminal and shrink it in place, it makes an excellent cover. And a smaller piece of tubing will work well to cover the crimp connection on terminals that don't come with built-in insulation.


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.

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! He recommends it be used on all connections, fuse blocks, switches, etc.

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.

Wiring Harness Renovation

Richard O. Lindsay sends this innovative method:

Tie the harness into position with tiewraps thereby preserving all of the original bends and more importantly, breakout 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 colorcorrect 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 counterclockwise 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 ClassTech of Bend, Oregon, 1-800-8749981. The second shop was Harnesses Unlimited of Oreland, PA, (610) 6883998.

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 heatshrink 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 rewrapping.


The UK uses a different definition of the rating for fuses than the U.S. does. The U.S. 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. 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 U.S., that is. It states that "English standards differ from U.S. standards. This accounts for difference in ampere ratings." Then it provides a list:

Englist 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  7.5

 5 amp

AGC  3


There are relays all over the XJ-S. Most are a Bosch 12V 30A SPST relay, and are a small metal box with spade connectors 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.

These relays conform to a standard, and are readily available at any auto parts store. Often, the aftermarket relays are labeled 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, any aftermarket electrical device is likely to be as good or better than a British original.

Some of these relays (and apparently ALL of the aftermarket generic equivalents) have a second connector 87 in the center of the base. This connector is connected internally with the first 87, regardless of relay operation; it merely serves as a second connector to the same terminal. In most cases, a relay with the extra spade connector 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 connectors 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 connectors where it is needed.

Radiator Fan Relay

A notable exception to all of the above is the radiator fan relay, SRB411. This relay has the exact same layout of spade connectors on the bottom, except that the connector in the center is labeled 87a. This relay is bright red -- Lucas' way of indicating "Hey, dummy, this relay is DIFFERENT!" (any intelligent design would have had a completely different spade connector layout to prevent any possibility of confusion, but remember -- this is Lucas we're talking about). 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.

Worse, 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 connectors 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 special relay without a good reason.

Even though a generic driving light relay won't serve here, finding a 12V 30A SPDT relay is usually not 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 VF445F11. Per Volker Nadenau, the Hella part number is 4RD003 52013. "It fits without any modifications in the red Lucas socket."

Or, you can go to an electronics store and buy a generic "ice cube" 12VDC 30A 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.

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 connector 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.

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 connector, 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.

Starter Relay

Dick Broxon of Cincinnati reports that his 1988 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.


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 V-12's, and is smaller, lighter, more reliable, and just all-around better.


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 12volt 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 reportedly offers a bracket to fit a GM alternator, complete with a suitable wiring connector.

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 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.

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

Alternator Load Dump Module

Reportedly, the 115 amp alternators fitted to the late 1980'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.

Electric Cooling Fan

Yes, it's atrociously expensive. But it doesn't do anything any other 12V, 11" diameter electric fan won't do; substitutions are in order. A Subaru fan will work with minor blade trimming and a homemade mounting adapter plate. The bad news is that a Subaru fan ain't cheap either, but at least it can be found in a common junkyard. An aftermarket 11" fan (perhaps J. C. Whitney cat. no. 38-3020A, US$57.98) could also be used with a little ingenuity. Be sure to include a system of rubber mounts, similar to the Jag originals, to minimize noise.

Better yet, ditch the electric and belt-driven fans and install two large electric fans in front of the radiator.

The stock wiring system for the small electric fan incorporates a bootstrap circuit. If the engine is off, there is no power to the electric fan or temperature switch and the fan cannot start. However, if the fan happened to be running when the engine was shut off, the bootstrap circuit provides power to keep it running as long as the temperature switch calls for airflow. As soon as it shuts off, it cannot start again.

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 'bell' 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 'bell' shaped tin cover so it is easy to poke a hole in it. Then just take a 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 'flood' 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 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 III 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 Series 2 E-Types (and probably XJ-6s of the same vintage) used 80 psi gauges while the V-12s 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.

Electric Windows

They always move slowly. This tip is from Leonard Berk of Howard Beach, NY: 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.

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 and the others had become loose. The motor assy. would move when you raised or lowered the window. After tightening the screws and 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.

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.

By the way, 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.

PS: On my car, the side with the new channel opens and closes amazingly quickly. What a pleasure. The other side, with channel felt on the ragged edge (i.e., no more adjustment possible) takes much longer and occasionally hangs up.


The switches are always acting up.

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.

It is possible, however, that both the slow 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.

One 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, in my opinion 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 at 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.

Another 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. Two relays will be needed for each window, an "up" relay and a "down" relay, and each will need to be a double-pole relay with serious contacts -- at least 10-amp rating. Since the current needed to operate the relays is minimal, the switches should last forever even if they've already been abused and cleaned up a couple times. A massive power wire should be routed to the relays directly from the power bus on the firewall or some other heavy-duty source (any big, fat brown wire); you can toss in an inline fuse for safety. See Figure 8.

Figure 8 - Relay Addition for Window Circuit

The way electric windows work is that the motor 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 relays should be wired to do the exact same thing.

The relays can be located anywhere between the switch and the motor. Within the door itself is one possibility; 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 even 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, avoiding having to remove the door panels; you can intercept the wiring near the door hinge. The relays can even go within the console if preferred; I personally would not choose this location, because it reuses too much of the original wires from there to the door, and I think those wires are too small.

If the window switches were operational before the relay installation, it won't even be necessary to open the console. Wherever you are installing the relays, simply break into the RG and GR (right side) or RU and GU (left side) wires from the rocker switch to the motor. Wire in the relays as shown.

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 relay under the right 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.

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 US$85 each for the two of them. The following is a replacement scheme that works better. Note that for 1992 the joysticks were replaced by a fancy electronic adjustment scheme, and the following does 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.

  1. Make a flat rectangular panel to replace the original chrome escutcheon (see Figure 9). 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. Buy four switches, catalog no. 275-637 from Radio Shack ($3.69 each).
  3. You may also want to buy some Molex connectors while you're there, such as 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 10. Note that each wire connects to two terminals.

It may also be possible to utilize the mirror switches from some other car. More and more cars use electric mirrors these days. Figure 9 - Panel for Mirror Switches Figure 10 - Electric Mirror Switch Wiring


When your battery needs replacing, you will find that the XJ-S uses an unusual battery -- and that Jaguar wants $200 for it. 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. Worse, batteries emit hydrogen gas when charging, so you run the risk of blowing the trunk lid off your car. The Jaguar battery comes with an enclosed vent connected to a tube to route the vent out through the floor of the trunk.

A standard battery can be made to serve, but you must 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)."

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

Michael Neal suggests a battery made by Optima. This is a leadacid unit but uses six separate coils instead of plates; it uses a gel electrolyte and is reportedly sealed, no vent required. "So far they have proven nearly indestructible." It is about $120 with a 6-year warranty, free replacement within the first two years.

Delco Freedom batteries come with a vent/cap assembly that has two vent openings. Each is sort of a flat oval shape, but it may still be possible to connect tubing to them.

With careful selection, the vent cover from the old Jaguar battery can be used on a generic replacement battery. Georges Krcmery says:

The EXIDE MegaCell # E42 50W has a rectangular slot around it's 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.

Winter Storage

Herbert Sodher hails from the cold North where people store their Jaguars all winter and drive less valuable vehicles in the snow. When stored that long, the battery in the XJ-S tends to go dead. The alternator, clock, and some stereos and security systems put a small drain on the battery when the car is parked. Jaguar recommends disconnecting the battery if stored more than a month, but that may be assuming too much about the condition of the battery and how easy the engine will be to start. And, disconnecting the battery requires resetting the clock, all the stations on the digital radio, and possibly some security stuff, all of which is a pain.

Sodher suggests the owner go to an auto supply store and purchase an on-board, fully automatic trickle charger and install it in the car. One called the Mity-Mite is made by Schumacher Electric Corp., is rated at 1.5 amp, and costs around $30. This unit is so small that Sodher attached it right to the front of his battery with Velcro, and the battery cover will fit over it (his battery is not the original -- it may require a different location for the Jaguar battery). It comes with eyelet connectors that can be connected directly to the battery terminals. Merely remove the nut on the clamping bolt from each terminal, put on the connectors, and reinstall the nuts. The unit comes with a one-foot power cord, just enough to feed outside the battery box. When parked for extended periods, merely run an extension cord into the trunk. The unit will automatically charge the battery as required, and won't overcharge it.

Windshield Wipers

Wipers Not Parking

If your wipers don't park, you may be tempted to start tearing the wiper motor apart to work on the parking contacts -- but you would be forgetting that this is Lucas you're dealing with. As Mark Roberts found out, the problem is every bit as likely to be within the stalk switch.

Because the wipers would park in intermittent mode, I was skeptical about the problem being with the parking micro switch, but checked it anyway. Micro switch was fine. The problem was traced down to the stalk switch. In the off position, pins 5 & 6 (ULG & BLG respectively) are suppose to be shorted together, to provide a ground path for the motor. They are also supposed to be shorted when in intermittent mode for the same reason. On my switch, 5 & 6 were shorted in intermittent mode, but OPEN in the off ground, no work.

Parking Position Adjustment

For some reason, the XJ-S wiper pivots are symmetrically located, so the driver's side wiper bumps into the windshield frame when parked. To solve this, the official adjustment scheme is to adjust that wiper to park up high so it doesn't hit the frame, but it looks stupid -- and is right in the driver's face. Just to make sure you're aggravated, the wipers park on the right in countries where they drive on the left, and vice versa; it's always in the driver's face.

One workable solution is to modify the driver's side wiper arm to be shorter. This requires carefully unfolding the sheet metal where it is wrapped around the strut, and drilling out the rivet just above the spring attachment. Then the strut can be cut about an inch shorter, drilled and bent to form a new spring attachment, a new rivet hole drilled, and then the strut can be reattached with a new rivet (a pop rivet will do) and the sheet metal re-crimped around the strut. A little flat black paint, and no one will know the original design was so poor. With the shorter arm, the left wiper can be positioned much closer to the bottom of the windshield. Note that the shorter wiper will not reach as far toward the top of the windshield either, but this doesn't seem to pose a problem.

Another possible solution is to alter the wipers so they park on the passenger's side. In the case of the later Electrolux motor, Stefan Schulz says this can be done by merely opening the motor gearbox and moving the park cam 180 degrees; it might be possible to make a similar change on the earlier Lucas motor. Or, you could arrange to buy a wiper motor from another country, or even trade with somebody in that country who's trying to make the same fix! You will need to purchase Jaguar wiper arms that have the little bend the opposite direction. Of course, after all this the wipers will still be just as obtrusive, but they will be aggravating the passenger instead of the driver.

Motor Durability

A design problem with the Lucas wiper motor is that the drive gears at the wiper arm shafts are plastic. Wear is a reported problem, and can be aggravated by operating the wipers on a dry windshield. It is suggested that the XJ-S owner use Rain-X or similar product on the windshield on a regular basis. This will make the water run off so the wipers need not be used as often, and it will also make the surface of the glass more slippery, so the wipers move more easily.

Note that 1987-on cars may be fitted with an Electrolux motor; this unit has metal gears at the wiper arm shafts. Stefan Schulz says

The parts guy at my local Jag dealer says that it is not a drop-in replacement for the Lucas one.

Wiper Arm Mount

The wiper arms are mounted on the shafts with a taper fit, held tight with a nut that is covered with a plastic clip. However, the base portion of the arm is made of aluminum, and a slight growth or wallowing of the tapered hole is an occasional problem. Contrary to expectations, this cannot be dealt with by merely tightening the nut further. The nut bottoms on a shoulder above the taper, and the arm remains loose.

This problem can be easily corrected. Cut a piece from thin sheet aluminum (old real estate signs work great!) and roll it into a conical shim. Installed between the shaft and the arm, it will provide a tight fit.

Directly under this joint is supposed to be a piece of rubber that looks like it might keep dirt and water out of the bearing. If this seal is rotten or missing, you probably won't wanna pay Jaguar for a new one. Reportedly, a visit to a hardware store should provide choices for substitutes; there are many parts shaped more or less like this, notably in the plumbing stuff - valve parts and seals, etc. You might have to do a little cutting.

Wiper Motor

The housing of the wiper motor consists of a cylindrical can with covers on each end. The cylindrical can has a notch cut at one end to form a drain hole to keep water from collecting inside the motor. Unfortunately, the drain hole is not at the bottom! To correct the problem, Jaguar provides a plastic cover over the motor to keep water from getting on it.

If you have trouble with the wiper motor, proceed as follows:


Removing the wiper motor involves removing the entire intake grille assembly in front of the windshield. It doesn't look hard, but there may be trouble; the two fasteners closest to the windshield actually involve a rubber isolation mount, and trying to unscrew the nut may just rip the mount apart if you are unlucky today. Fortunately, it isn't too difficult to improvise a replacement mount scheme using a small bolt, a couple nuts, and a rubber grommet or two. It probably wouldn't be a good idea to rigidly mount the grille, though; Jaguar probably used the rubber mount for a reason.

Disassembly and Repair

To repair the wiper motor:

  1. Mark the housing before taking it apart. The parts must line up the same way when reassembled. Also, mark where the bottom is as installed in the car.
  2. Clean up the internal parts, especially the brushes, which tend to jam when they've been wet for a while. Make sure the brushes slide freely.
  3. Cut an additional notch in the housing, this time at the bottom.
  4. After reassembly, it wouldn't hurt to cover the top of the motor with aluminum tape (available where air conditioning supplies are sold -- it's used to seal ductwork) to help prevent water from getting in.

Of course, providing a new plastic cover over the assembly would help for a while. Notice that the assumption was made here that the original is no longer on the job. Yes, it's junk. The aluminum tape in step no. 4 is likely to be the prime protection in the long run.

Chuck Roach says:

I went to my Jag dealer to pick up a new cover and the parts/service manager told me to forget it and just use an old one-gallon plastic bottle and cut it to fit and hold it in place with cable ties. Worked great. Will probably last as long as the original.

I disagree; it's likely to last a good deal longer than the original.

By the way, if you're wondering where the original cover went, you need to read about water leaking in through the A/C system.

Light Bulbs

If you have WWW browsing capability and a credit card, you can order whatever bulbs you're ever likely to need from:

Thanks to Richard King for this tip.

Indicator Light Bulbs

The tiny bulbs used in the row of indicator lights at the top of the dashboard can be found at any Toyota dealer. Best to take the old one to show the parts man what you need, since he's only familiar with Toyotas and doesn't know what a Jaguar indicator light looks like.

Turn Signal Bulbs

The stock bulbs are generally only available in the UK, but of course the standard 1156 and 1157 bulbs will fit. However, if you try to use 1034 bulbs, the indicator on the dashboard may only light the first blink, or not at all, when you operate the turn signals. This is the bulb failure indication for the turn signals. Since the 1034 bulbs are lower wattage, the reduced current causes a bulb failure indication.


If you have WWW browsing capability, you can learn everything you need to know about headlights in general at:

Thanks to Richard King for this tip.

Headlight Brightness

Jon Jackson and others point out that dim headlights may be the result of bad grounds.

On my 1987 XJ-S there is a ground under the hood to the left side of the radiator. There are several ground wires that go to this same point. Cleaned it up a bit and all is great.

Headlight Wiring

The headlight and fog light wiring diagram in the Supplement to the Repair Operation Manual, copyright 1982, is too screwed up to follow. Figure 11 is a replacement for the diagram, based on an actual 1983 H.E.; note that if your wiring matches this schematic it is impossible to operate the fog lights (see Fog Light Wiring, below). Figure 11 - Headlight and Fog Light Wiring

The headlight switch in the 1983 H.E. has five positions, three above and one below the off position. To get into the top or bottom position requires pushing the knob in while turning. The connections made in the positions are as follows:

3: 1-2-3-5

2: 1-2-3-4

1: 1-2-3

0: No connection

-1: 1-2

The -1 position, connecting only the dash lights and right side parking lights, apparently serves no intended purpose; as wired, all the parking lights come on due to backfeed through the bulb failure sensors. After a few seconds for the bulb failure sensors to warm up, the left side parking lights dim. If an owner wished, however, it would be a simple matter to rewire the right side parking lights to terminal 3 and use the -1 position to operate the dash lights only.

Headlight Switch Knob Removal

To remove the headlight switch knob, you must depress a button in the shaft that is behind the surface of the dashboard and points down. To reinstall, you merely need to push the knob on, because it is shaped to slide over the shaft button and snap in place.

High/Low Beam Relay

In some manuals, the schematics of the high/low beam relay (Jaguar part no. C38616) show the components between connections 56, 56a, and 56b to be a normal set of relay contacts. This is NOT actually the case. This device is an electrically-operated rocker switch; when the coil is energized, the contact is switched from one side to the other, and remains there when the coil is de-energized. Figure 12 - High/Low Relay Replacement Scheme

If your high/low relay has given up the ghost and you don't like the price of a replacement, an alternate scheme using 3 relays and a diode is shown in Figure 12. Note that wiring (and related contacts) indicated by heavy (red) lines must be suitable for headlight current, 30 amps or so. All other circuits are less than 3 amp. For the diode, a Radio Shack cat. no. 276-1661 will do nicely. Of course, you will need to figure out where to mount these relays; perhaps in the space behind the left headlights.

As with any such circuit, a single multi-contact relay may be replaced by multiple single-contact relays by simply wiring the coils together. This may make sense here, allowing the use of SPDT 30-amp relays along with tiny "ice cube" DPDT relays instead of trying to locate DPDT or 3PDT 30-amp relays.

The only functional difference with this circuit from the original is that your headlights will always be on low beam when you first turn them on.

Fog Light Wiring

If your fog lights don't work, you may not be alone; some don't work because they were wired incorrectly from the factory. Apparently, in some countries Jaguars are fitted with "fog warning lamps" at the rear of the car; the top position on the headlight switch turns these rear fog lights on. The front fog lights are operated by a "fog lamp switch." The 1983 XJ-S (American version) has no rear fog lights, and no fog lamp switch. The top position on the headlight switch sends power to unused connectors at the rear of the car, and there is no way to turn on the front fog lamps.

The fog light wiring can be corrected by simply reconnecting a wire from fuse 1 to fuse 6. Be sure to leave the existing wire on fuse 6 connected to operate the dash indicator. With this system, the top position of the headlight switch will operate the fog lights and the low beams; high beams are inoperable to avoid conflict with some state laws.

If you have genuine fog lights (yellow lenses), it usually makes sense to wire them so that the fog lights can be operated without any headlights. This would optimize visibility in foggy conditions, where the headlights simply cause glare. The rewiring scheme shown in Figure 13 causes the fog lights only to operate on the top position of the headlight switch. Although the inhibit relay is shown disconnected, it would be just as well to remove it entirely in this scheme, as it serves no function. Figure 13 - Rewiring For Fog Lights Only

It is possible to rewire the Jag so that all six lights work at once; this makes sense if the car is fitted with driving lights instead of fog lights. The suggested scheme (shown in Figure 14) is designed such that in the top position of the headlight switch, both the driving lights and the high beams operate as high beams, and the low beams remain unaltered. Two new relays (30 amp contacts) are needed, and a new 12V supply circuit is called for.

When installing these relays, it is convenient to install the one on the left in the drawing near the high/low relay at the front left of the engine compartment, as all the necessary wires are nearby; the harness will have to be opened to get at the red/yellow fog light wires. The relay on the right should be installed under the dash, as its wires are convenient there.

The reconnection at the inhibit relay is very easy, because Jaguar ran the appropriate wire to an unused port in the relay socket just for you. All you have to do is remove the blue and the blue/red wires from the socket and reverse them.

The scheme will also work if the new relay on the right in the schematic is omitted, no new 12V supply is run, and the circuit is left connected to fuse #6. However, the system shown is suggested to avoid overloading any existing circuits -- especially if you install high-powered driving lights.

In many states, there have been laws that prohibit there being more than four headlights on a car. Jaguar's intention for the inhibit relay was to prevent use of the high beams while the fog/driving lights are on, thereby complying with the law. It is unknown how these laws have evolved now that the law requiring standardized headlights has finally been eliminated (thank God!) so Jaguar can use the European single headlight assemblies here in America. The owner is advised to check his state's current regulations before rewiring for all six lights to operate at once as shown above. Figure 14 - Rewiring For All Six Headlights At Once

Driving Lights

If you wish to replace your fog lights with driving lights, or have destroyed your original driving lights, J. C. Whitney catalog number 14XX9739Y is a good choice. These lights look good, have a similar appearance to the originals, have a rustproof plastic housing -- and the box they come in has an illustration of an XJ-S on it!

There are many excellent driving light kits on the market, and almost any of the rectangular style can be fitted to the XJ-S and will look proper. It's a good idea to check on the availability of replacement lenses, since they are prone to damage. WalMart and AutoZone offer kits with the replacement lenses for sale right next to them on the rack! You can also check to see if the lenses are thick and substantial to resist all but the most powerful impacts.

Most driving lights use an H3 bulb; standard wattage H3 bulbs as well as high-power bulbs are readily available.

Headlight Buzzer

The XJ-S doesn't come with one! What a cheap car. To add one is easy. You need a 12 volt buzzer such as catalog no. 273-055 from Radio Shack, and a rectifier (or diode) such as catalog no. 276-1661. For the buzzer you can also use any buzzer you've ripped out of a car, such as those pesky seat belt buzzers.

Connect one of the headlight wires to one end of the rectifier. Connect the other end of the rectifier to one lead of the buzzer. Connect the other lead of the buzzer to one of the ignition wires. Both of these wires are near each other under the dashboard -- from the headlight switch and the ignition switch.

A rectifier allows current to flow in only one direction. If you have wired it correctly, when both the ignition and the headlights are on, there is no current flow because both wires are at 12 volts. When the ignition alone is on, there is no flow because the rectifier stops it from flowing that way. When the headlights are on but the ignition is off, current flows and the buzzer buzzes. If the buzzer buzzes when the ignition is on and the headlights are off, reverse the rectifier.

Jan Wikström did it a different way:

Pulling the key out also operates the switch that controls seat belt warning etc. As my car doesn't have those, I've used it to operate a "headlights on" warning buzzer.

Bulb Failure Units

There are bulb failure units in the trunk right next to the trunk lights, as well as under the right side dashboard. The Supplement to the Repair Operation Manual says there is only one under the dash to serve the lights on the front of the car, but it lies; there are two, one serving the front right and one serving the front left. They all look the same: a small metal box with three connectors. The current to a light goes in one connector and out another, heating up a conductor inside. When it gets hot enough, a bimetal strip bends enough to break the third connection to the dash indicator. This is why it takes a few seconds for the indicator to go out when you turn on the lights. If a bulb burns out, the reduced current doesn't heat the bimetal strip enough, so the indicator stays on.

If your dash indicator is staying lit for unknown reasons, the first thing to do is check that all the lights on the car are of the correct wattage (see below). A lower-current bulb can fool the units. Then, find each unit and disconnect the indicator wires (WS) one by one until you find which unit is keeping the indicator on.

If one of the units isn't working right, they can be adjusted. There is a tiny screw on the box near the connectors, sealed with a drop of glue. When you're absolutely sure all the bulbs are working right, leave the lights on for a couple minutes. Turn the screw clockwise until the dash light comes on, then counterclockwise just until it turns off. Be careful not to touch ground with the tool used to adjust the screw.

There is a different type of failure sensor on the brake lights, but it operates the same dash indicator. With the ignition on, headlights off, handbrake applied, and the brake pedal pressed, the indicator should come on; if it does not, there's a bad circuit or bulb in the brake lights.

The indication that a turn signal bulb has failed is that the turn signal dash indicator just blinks once, or not at all, while the functional bulbs on the outside of the car continue to blink properly.

Third Brake Light Bulb Replacement

It may not be obvious at first, so John Himes sends this description for getting to the bulbs:

Feel or look on the underside of the cover; there are 2 black indentations on each side of the cover. Place your fingers on each of these, or you can also do one at a time. Press up on the indentation which is a sprung black square button that keeps the cover from rattling off. After your remove the cover, you have access to the bulbs. They are in gray plastic holders that you turn 1/2 turn to release.

Gauges Reading Low

Brian W. Rice writes:

All gauges in my 1985 XJ-S read low by 25% when I acquired the car several years ago. I did some tests by lifting No. 4 fuse and applying a variable voltage to the dead end from a power supply, making sure not to exceed 15 volts. With precisely 12 volts applied the voltmeter showed about 9 volts. The fuel gauge also only indicated 3/4 with a full tank of petrol.

I removed the instrumentation panel, quite an easy job, and investigated on the bench. All gauges showed corrosion at the rear terminal nuts and washers where they contact the flexible printed wiring assembly. I was able to repair by soldering tinned copper wire to the flexible circuit board tracks being careful not to melt the plastic flexible board and fashioning the wire into circular washers to go under the terminal nuts thus establishing good contacts again. Gauges now work as designed.

Radio Removal

Steve Broady, regarding the late-1980's radio:

Assuming your radio is a Blaupunkt made in Korea, you will need to cut a coat hanger into 2 pieces like a pair of U's to push into the front plate holes to remove radio from bracket. When you pull the radio out of the dash watch for ground strap on left side as bolt protrudes into bracket. Once out you will find 2 live input wires with fuses; one is for clock and code function, the other for radio, tape, antenna.

Radio Security

According to Greg Meboe:

The 1986 Jags came with the removable-face tape deck, a design which has made radio repair/replacement outfits a lot of money due to its low service life. The face comes off to ward against theft, but the connectors for the face don't seem to cut the mustard.

Somewhere around 1986, Jaguars came with a radio that had another security feature: if the power was disconnected, the radio would never work again unless the correct security code is entered. Presumably, people who steal radios won't steal one they can't use.

Of course, you can choose any repair procedure in the manual, and chances are the first step is to disconnect the battery. If you already went through this and your radio is now nonfunctional (or you have stolen such a radio), you apparently will need to contact your friendly dealer to obtain the security code. You may also need to provide a serial number that begins with "B" that is on the case of the radio.

If you would like to avoid the grief, reportedly there is a product on the market that can be plugged into the cigarette lighter. It uses a 9V battery, and will keep a small amount of power on the system while the battery is disconnected. It will supposedly keep the radio operational, stations programmed, etc.

Condensation Deflector Shield

Apparently, either plugged condensate drains in the A/C system or leaking heater cores have a tendency to dump water on the stereo -- and some of those stereos ain't cheap! So, Technical Service Bulletin #8685 says essentially that a "condensation deflector shield" MUST be installed on all XJ-S vehicles prior to VIN 163790 whenever the mechanic is working in the area. The part number for the deflector is CBC 9193, and it appears to be VERY easy to install, requiring only 0.10 hours.

Brake Fluid Level Switch

The switch in the cover for the brake fluid reservoir is supposed to light an indicator on the dashboard when the level is low. The rubber cover over the connectors has a bump in the center. Pressing the bump forces the float downwards and closes the contacts, providing a circuit and bulb test.

Unfortunately, the switch is garbage and the indicator may never come on, or may stay on all the time. The float for the switch is a piece of cork, which rots, soaks up fluid and sinks, etc. The protective metal cover over the cork float gets full of junk and jams the float. The contacts within the switch, despite evidently being silver plated, get corroded and fail to make a connection.

An acceptable method of correcting this switch's problems has not yet been developed. The cork is easily replaced with one from a wine bottle, and the metal cover's problems are solved by removing it. The contacts themselves can be serviced by using a tiny screwdriver to pry the switch assembly out of the top of the reservoir cover; don't lose the little metal sleeves that keep the contact screws from tightening down onto the plastic.

But this switch needs to be ultra-reliable, since it is rarely tested and failure to work when needed can be disastrous. While it's easy enough to get it working with the procedures above, there's no apparent way to get it to keep working. At this point, it can only be recommended that XJ-S owners avoid trusting the indicator and check their brake fluid level frequently -- and check the operation of the switch frequently, too.

Glovebox Light

The XJ-S doesn't have one! What a cheap car. It's easy enough to install one, though. Just buy a suitable light fixture at your favorite auto parts joint, and install it in the top of the compartment just behind the latch. Wire it into the interior light switch just to the left, so when the switch is operated it will turn on both the right front interior light and the glovebox light.

Cigarette Lighter

Apparently, some XJ-S's were equipped with some sort of non-standard cigarette lighter. This causes two problems: first, when the element in the lighter quits working, it's hard to find a replacement; and second, it may prove difficult to plug non-cigarette-lighter accessories into the cigarette lighter hole. If you are having either of these troubles, the easiest solution is to drop by any auto parts store and buy a generic cigarette lighter and install it, and throw that hokey Jaguar one out.

Radio Antenna

Adjusting Drive Clutch

Steve Leamy sends instructions on adjusting the drive clutch:

This repair covers ant that just wont quite make it up or down and still makes a clicking noise before stopping.

You want to get to the side of the unit that looks like a cup and has a screw in the middle of it. Remove the screw and the cover and you will have now exposed the clutch drive for the ant. On the shaft in center you will find a locking nut which you will now back off 1 or 2 turns, now grip the metal clutch and tighten 1/2 turn. Retighten locking nut and prop unit up so you can test it. Turn key on and radio and ant will raise in 15 to 20 seconds, once ant reaches full height you should hear 3 bumps and ant motor should shut off. Turn key off and ant should go down completely and 3 bumps and motor will cut off. If ant still does not go full up or down adjust clutch in quarter turns until a full stroke is attained.

On 1988 and above XJ's I have found three different manufacturers of ant in the cars I have serviced the but all of them use some type of clutch system and can be fixed by resetting of the tension on it.

Some models use a plastic drive wire instead of metal; you can repair these with weed eater line but you have to remove the motor base and ant to service it.

Antenna Repair Kit

A repair kit is available for some Jaguar antennas, including the mast and the plastic gear rack. According to Hal Rogers of H. D. Rogers & Sons:

It depends on which Jaguar... i.e., which antenna assembly that you have. A replaceable mast is available for the Hirschman brand antennas...the mast is the same for some German cars. The Jaguar equivalent part number is DBC2200. Mostly late 1980s-up cars...

Next, if you have an older Jaguar, they had a Japanese manufactured antenna. It does not have a replaceable mast, never did. The unit that we sell which is a replacement unit, not exactly the original, and you may need a fitting kit as well...It replaces DAC3542 or DAC4090 Jaguar part number.

There is not a real easy aftermarket replacement for the late Hirschman...though you can change the mast.

Also, see Jaguar All-Parts.


The original Jaguar antenna is incredibly expensive, even when the mail order shops put it on sale. If you're not real concerned about maintaining the appearance of the inside of the trunk, you can replace the antenna and its delay relay with catalog number 03-9579A from J. C. Whitney for US$35. It doesn't have that 10-second delay before going down, but nobody's ever figured out what that's for anyway.

Connect the green wire from the antenna to the white/pink wire in the car. Connect the red wire from the antenna to the brown wire in the car (brown wires are the generic Jaguar 12V power wires). Make sure the housing of the antenna motor is grounded to the car, either by the mounting scheme or by connecting the black wire to it. Also, this antenna has a drain tube to dispose of rain water that runs down the antenna into the housing; route the drain tube somewhere outside the car.

The antenna installation instructions also direct you to adjust the antenna trimmer on the radio. However, if your radio has an electronic tuner (digital display instead of mechanical needle), it probably has no such adjustment.

This is not the only antenna available that can be made to fit this car, and in fact a suitable replacement can probably be found at most auto sound system shops. Be sure to ask for a "fully automatic" model; don't get one that you have to press a switch to raise and lower it.

Tom Graham put a Radio Shack antenna into his Series 3 XJ6, but it looks like the same would work for the XJ-S

...Radio Shack, number 12-1330A. It works, including the delay retraction.

As compared the Jag unit which has the telescoping tubing in the fender well and the motor in the trunk, the RS unit is all one unit. Thus it all must fit into the same fender area as the Jag's telescope unit.

Start by taking out the Jag unit. When you pull out the Jag motor assembly it has three electrical connections. The ground strap is obvious. A blue/white wire runs to the motor relay and a blue/red wire runs to the motor relay. We will use the relay connection for the blue/red wire to control the RS antenna.

The electrical connections are relatively easy. The RS unit has three electrical wires, one black, one orange, one red (and the antenna). The black wire is ground. The orange wire controls the antenna motor thus making the antenna go up or down. That is, when the orange wire has voltage on it, the antenna raises. When voltage drops off of the orange wire, the antenna retracts. Connect this orange wire to the original Jag antenna motor relay, where the Jag wire blue/red was. Do you remember where the blue/red wire was on the relay - it is in the middle of all the connectors (NOT the top outside one, that was the blue/white wire). HOWEVER, my Jag "electrical schematic" shows these wires reversed. Better check yours. The Jag relay spade connector we want will have voltage (battery) on it when the radio is on. Check this with a volt meter to chassis ground. Then turn the radio off, the voltage will drop off in about 15 seconds (this is how the delay works). Connect the RS orange wire to that relay spade connector. The RS red wire is for power to the antenna motor, it comes with a 5 amp inline fuse. Connect this red wire to the (brown) wire. This completes the electrical wiring of the RS unit. You will note with pleasure that the antenna still has the delayed retracting feature of the Jag.

It appears that the Radio Shack and J. C. Whitney power antennas, and probably most of the other ones on the market, work pretty much the same way; there is a ground wire, a power wire, and a signal wire. Simply select one that will fit in the space. The major difference between the two installations described is that Graham chose to keep the original Jaguar antenna relay in the circuit to maintain the delay, and this method would probably work just as well with any other aftermarket power antenna.

Roller Microswitches

The microswitches on the throttle linkage and on the shifter look tricky with their little rollers and all. However, they are in fact a standard item, and are readily available at your local electronics store -- complete with identical rollers.

Trip Computer Fuel Mileage

The CATALOGUE reports that erratic fuel mileage readings can be caused by a poor connection at the fuel injector resistor pack. The fuel gauge readings are unaffected.

Jaguar Diagnostic System (JDS)

Later Jaguars are fitted with connections for an electronic diagnostic system. A knowledgeable mechanic, who shall remain nameless here, sends the following words:

JDS stands for Jaguar Diagnostic System. Basically it is a processor that ties into the serial ports in the car wiring. However good this may sound, it is no more than a glorified wiring diagram. It sends you down the circuit you are checking and you end up more often with a car that is torn apart and not fixed. All Jaguar dealers in the U.S. were forcibly recommended to purchase one of these US$23,000 units back in the late 1980's.

The new P.D.U. diagnostic unit which is supposed to be the new JDS is a self-contained unit that can be taken on road tests. Gen Rad is the manufacturer of both of these machines. The P.D.U., already dubbed as "Pretty Damn Useless", is a very complex unit. It uses CDROMs instead of 3.5 floppies. The screen is about 4" square, green display. It is a very difficult unit to use. The techs that have been to school for the P.D.U. still have very little understanding of it.

Seat Heater

Later XJ-S cars come with a seat heater, and apparently it lacks reliability. Stefan Schulz sends a description of the repair of this unit:

The seat is connected to the car electrics through three different connectors, one for the seat belt logic (cable runs under centre console, pull carefully to expose connector), one for the lumbar pump, and one for the seat heater. The latter two are under the seat and can be accessed most easily by moving the seat as far to the rear as possible.

Having disconnected the seat heater connector, check with a voltmeter whether it delivers power when the seat heater is switched on. If it does, the problem is somewhere in the seat. Remove seat.

Turn seat upside down in a clean area. Locate the connector that connects the bottom seat heater in series with the one in the backrest. Pull it apart. Use an ohmmeter to figure out whether the bottom or the backrest heater is faulty.

If the bottom heater is faulty, remove the black rubber cover from the bottom of the seat. See where the heater power supply wiring enters the bottom cushion? Good. Carefully pull it apart at that point, exposing the top of a cheap and nasty heater element.

Cut the top covering of the heater element to one side of the thermostat and flip it over to the other side to expose the thermostat element. Don't cut it away, you'll need to put it back later.

There are three joints within the seat heater element. Orange/slate wire to thermostat, thermostat to heater element, heater element to black wire. Examine all three joints. Note that they get hot (hey, they're part of a heater) and are moved and flexed constantly. Solder joints should never be used in areas that get hot or which are under mechanical stress like the one these wires are experiencing. So what did the cheapskate Jaguar designers use? Exactly. The thermostat is cheap too, and its connection lugs will be badly oxidized.

Take out the thermostat and subject it to the usual boiling water/ice water routine to test it. Check with an ohmmeter that it opens when in hot water and closes when in cold. Being more precise with a cheap part like that is a waste of time. If you find that the thermostat is faulty, you'll see that it is not a Jaguar part. Jaguar wants you to replace the entire heater and cushion assembly. But this 'stat doesn't do anything any other 45degreesC/12V/10Amp bimetallic 'stat wont do, so get a replacement from an electronics shop if necessary.

Solder the thermostat back in, using weaponsgrade solder wire with a high silver content and consequently high melting point. You did remember to dry and clean the connection lugs first, of course. Resolder the third connection (heater to black wire) as a matter of course.

Squeeze the thermostat back into the cushion, make sure that none of the heater wires touch it. Put back the top covering using solventfree glue and a staple at the end. If you use glue containing solvent, you will find that that works the same way as the naturally occurring rot of the seat foam, only a lot faster seconds instead of years. Use an ohmmeter to check the resistance offered across the seat heater connector now it should be about 1.8 ohms.

Refit all the other components by reversing the removal sequence. Put the seat back in the car and connect it (remember the seat belt logic connector!)

Boot Lock

According to Mike Cogswell, electric boot locks were introduced in 1989 models. According to his dealer, they cannot be retrofitted to earlier models.

Key Fob Lock

According to Mike Cogswell, the key fob security systems were introduced in 1989 as a dealer-installed option. Apparently these cannot be fitted to earlier models.


On to the Cruise Control


// JagWeb // XJ-S Help // Contents //


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