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Headlight Modifications

  Experience in a Book
Headlight Modifications


When you're driving your Jag down some desolate two-lane blacktop road at 140 mph on a moonless night, it's helpful to be able to see where you're going. Unfortunately, not all headlight systems are up to the task. If you have the US-spec four round headlights with the original sealed beam units in place, I suggest you slow down.

Even if you obey all posted speed limits, you will be amazed at what an adequate set of headlights will do for the pleasure and enjoyment of nighttime motoring. Where you used to have to squint and stare in hopes of seeing things in time to avoid hitting them, you can now sit back and relax. In fact, you may come to fully appreciate the advantages of nighttime driving, with the reduced traffic and cooler temperatures.


RELAY INSTALLATION: If you wish to improve the headlights on your car, the first thing you should do is install a set of control relays. This will improve the light output of the stock headlights, whatever type they are, and may just satisfy your need for better light -- and is a perfectly legal modification. If you do decide to replace your headlights with something with higher wattage (as in some of the mods described below) you will not be happy with the results unless you install control relays; the additional losses in the stock wiring due to the increased current flow will rob you of any increase in light output.

The whole idea of installing relays is to get as much of the battery/alternator voltage to the headlights as possible, since a small reduction in voltage makes a big reduction in light output on incandescent lights. Low voltage also causes incandescent lights to appear yellowish, which diminishes visibility even more.

Your objective, therefore, is to provide wiring that gets the power from the battery/alternator to the headlights with big fat wires and as directly as possible. Unfortunately, that wasn't the objective of the guy who designed the wiring for your car; his objective was to provide wiring as simply and cheaply as possible, and sized just big enough to keep it from melting. So, the stock wiring goes from the bus on the firewall down to under the dash, through the headlight switch, back to the front left corner of the car, through the main/dip relay and the headlight fusebox, then out to the four headlights -- all with wires that are barely adequate for the sorry headlights that came with the car.

A simple confirmation of the problem is to remove the headlights from their mounts while leaving them connected, start the engine, turn on the headlights and measure the voltage right at the connections on the back of the bulbs. The voltage there should be within a half a volt or so of the voltage measured between the terminal on the firewall and the chassis under the same conditions (headlights on, engine idling). If the voltage is much lower, the installation of relays will help the light output considerably. If you'd like to confirm where the losses actually occur, measure between different points along the line, starting with the terminal on the firewall and including both ends of each fuse in the headlight fusebox as well as the terminals on the headlights. If you measure the voltage between the terminal on the firewall and the power connector on the headlight, you will be measuring the total loss of the wiring system except for the ground circuits. You can also measure parts of this loss, such as between the fuse and the headlight, between the firewall terminal and the fuse, even across the fuse itself. If you measure the voltage between the ground connector on the headlight and the chassis of the car, you will be measuring the losses in the ground wiring (which are significant -- the ground wiring is inadequate, too).

If your voltage losses are too high, the solution is to disconnect the wires from the headlights and connect them to the coils of relays, run a massive power wire from the terminal on the firewall to the common contacts on the relays, and run substantial wires (with suitable fuses) from the contacts on the relays to the headlights. Thus you operate only the relays with the original wiring, and the serious current for the headlights themselves takes a much more direct route from the battery/alternator through the relays to the bulbs.

This mod only requires the mounting of several relays and running a serious cable from the terminal on the firewall to whereever the relays are; this author used a 4 gauge, but a 6 gauge cable would actually be enough. The relays should be mounted somewhere near the headlights to minimize wire length; perhaps within the boxes directly behind the headlights themselves. John Napoli suggests a big fuse in that cable, since the relays are likely to be located out at the front corner of the car and may be shorted by a relatively minor collision, and the shorting of such a major cable may cause serious problems.

Technically, you can do this whole job with only two relays, one for low beam and one for high beam, but it may be preferable to use two for high beam to keep from overloading the contacts on a standard 30-amp relay. Of course, you'll probably want to install a relay for the fog/driving lights as well.

Having four individual fuses on circuits that operate nothing but relays is definitely overkill. On the XJ-S, it makes more sense to continue to use the existing headlamp fusebox to serve the headlights themselves, so the relays should be wired into the circuits before the fuses. If necessary, the headlamp fusebox can be fiddled with by drilling out the two rivets that attach the mounting bracket to the fenderwell. The bracket isn't welded to the flange on the edge of the engine compartment, just folded over it. Removing the rivets allows the bracket to be lifted away, which in turn allows the fusebox itself to be turned over and the wiring rearranged. You can reinstall the bracket with a couple of screws, making it easy to work on in the future.

Tip for those with the 4-headlight system: The existing wiring from the fusebox to the high beams on each side of the car is inadequate for both high beams, but it's close enough for one. So, one possibility is to run a new wire (about 12 gauge) from a new relay to each side of the car with a new inline fuse for one of these high beams and reuse the existing wiring and fuse holder for the other high beam. The small wire from the 3-prong connector right behind the headlights to the headlight that's getting a new wire should be tied back into the other headlight at the socket, so that both of these skinny little wires are serving one headlight.

This type of reconnection requires popping the spade terminal out of the headlight socket, soldering the second wire to it, and snapping it back into the socket. Each spade terminal has a little tang on the back that holds it into the socket, so you need to insert a pointy object between the plastic and the terminal itself to depress this tang to remove the terminal. You will also want to bend this tang back into position before pushing the terminal back into the socket, so it securely snaps into place.

Of course, when done changing which fuse serves which headlamp you might need to revise the fuse sizes in the headlamp fusebox. It's easy enough to divide the wattage of each headlight by 12 volts to determine the amps that it will draw, and install a fuse suitably sized to serve.

Be sure to provide adequate ground wires on the headlights as well. That's easy to do, by either adding additional wires or just replacing the ground wires entirely and connecting the new wires to a screw into the chassis, of which there are several handy right around the headlights.

While relay installation may involve a couple hours of fiddling, it is a very cost-effective improvement. The relays themselves typically cost less than five bucks each, and wire and fuses are also cheap.


UPGRADING HEADLIGHTS -- LEGAL CONCERNS: Before I delve into actual headlight upgrades, I'd like to explain a little about the evolution of headlight laws here in the US. Back in the 1950's and 60's, automobile headlights seemed like fertile ground for government control. Laws had been established requiring all cars to have one of two types of headlight systems: two 7" round headlights or four 5æ" round headlights. It was this requirement that ruined the appearance of the Jaguar XJ6, designed to have two 7" bulbs plus two 5æ"; for the US market, the two 7" had to be replaced with 5æ" with a filler ring around them. It also is the reason the early US-spec XJ-S has two round headlights on each side instead of the "Euro-style" single lamp assemblies.

Also, the light output of headlights was limited. And all headlights were required to be "sealed beam", meaning that the entire headlight was the bulb itself, when it burned out you had to replace the whole thing. The headlights also had to have three little bumps on the front, used to check alignment. On top of all this were general prohibitions on more than four headlights or six head/auxiliary lights on a car.

Sometime in the 60's they prohibited glass covers over the headlights. This changed the appearance of the Jaguar E-type and the Volkswagen Beetle.

In the early 70's, they added rectangular headlight systems to the approved list, basically allowing two arrangements of rectangular sealed beams.

With the advent of energy conservation concerns, the automotive manufacturers were finally able to convince US legislators in the mid 1980's to drop the requirements for using standardized sealed beam headlights and permit the use of "composite" headlight assemblies in the name of better aerodynamics. These headlights have a lens/reflector assembly that was custom-designed for the car (and usually atrociously expensive), and the bulb itself is a smaller quartz-halogen item that plugs into the reflector from the rear.

Unfortunately, apparently the US DOT couldn't be convinced to legalize the same composite headlights that were being used in Europe, so the US-spec cars got their own style of composite headlights. To this day, to be fully legal in the US, your headlight lenses need to say "DOT" on them. And most US-spec headlights seem to still have three little bumps for alignment even when the front of the headlight is sloped so some bumps are actually rearward from others. There are still limits on light output.

I dunno what DOT's priorities are, but it's obvious that they don't include providing good visibility at night or in rain. DOT-spec headlights suck, not to put too fine a point on it. And just to show that this is not a "grass is greener" thing where everyone thinks people somewhere else have it better, John Warr from the UK says, "You guys in the US have to drive with the most appalling lights I have ever come across. To someone used to Euro lights, the first experience of US lights at night in the rain results in a puzzled driver standing in front of his hire car trying to work out what he has not turned on."


E-CODE: While the US DOT conspires to keep drivers in the dark, the European standards for headlights have evolved based on input from major headlight and driving light manufacturers in an attempt to provide truly excellent lighting. Headlights meeting these "E-code" standards are indicated with a capital letter E and a number with a circle around it on the lens. According to Daniel Stern, the number indicates the country in which the headlight was certified to meet the code.

There are E-code headlights designed to replace any standard US sealed beam, and they always seem to have a distinctive pattern on the lens: there is a trapezoidal area between the center of the lens and the edge on the driver's side, with the fluting at an angle. These lights have a distinctive pattern on dip beam, sending light down to both sides and up towards the side of the road but not up towards oncoming traffic.

Stern maintains a site on the WWW that, among other things, describes the advantages of E-code headlights over DOT headlights in considerable detail:

Before jumping in and upgrading your headlight system, you might want to check the regulations in your state. Or, you might wanna simply note how many citations are handed out annually for illegal E-code headlight assemblies and decide whether or not you wanna chance it. Stern says, "The fact of the matter is that back in the '70s when all cars had sealed beams, E-code lamps stuck out like sore thumbs.  But today, with the proliferation of so many different headlamp designs, together with the elimination of headlamp inspections in at least 48 states, nobody knows or cares what kind of headlamps you're running." So, what's the bigger risk to you: getting a ticket, or being unable to see where you're going after sunset?

Stern also notes: "If you live in the US states of Oregon, Washington, Alaska or Massachusetts, or in the great nation of Canada, then E-code lamps are 100 percent legal."

Note that many of the "H4 headlights" sold by J. C. Whitney (page *) are actually low-end E-code units and are described as "for off-road use." That is how they can sell headlights that are technically prohibited on public highways in the US; why the upper left cutoff on low beam would be helpful in an off-road application is never explained.

There are a couple other tricks that have been used; when "sealed beam" headlights were required, J. C. Whitney sold some "sealed beam H4" headlights; the rubber boot had been glued on over the bulb socket making the whole thing sealed. When the H4 bulb burned out, you just cut the boot away and put in a new bulb.


FOUR ROUND HEADLIGHT IMPROVEMENT: If you have the four round sealed beam headlights, your headlights suck -- trust me on this. Daniel Stern suggests that one quick and easy improvement might be to merely replace the outer high/low beam units with H5009's instead of H5006's. These are 50/40W instead of the H5006's 35/35W. Unfortunately, they are apparently pretty difficult to find. "I can supply a lot of "unobtainium" bulbs, but not H5009's."

Another possibility may be the 50/50W H5812, "Althought now we're back to the theoretical, because H5812s aren't in current production."

You might consider replacing the whole assembly with the later oblong composite single lamps. This is an expensive change, however, and would probably only be considered by XJ-S owners who prefer the appearance. Since these headlights meet DOT specs, this mod should be perfectly legal in the US. Improvement? Stern says, "This is a tremendous, tremendous retrograde step in headlamp performance. The transverse-filament 9004 performs worse than many of the old sealed beams, even."

You might also replace the four headlights with one or the other of the Cibie single headlight designs used in Europe. Not legal on US roads, but will provide better lighting. Note that, if you get the Euro lights, you can also opt for the wiper/washer system for them, and even a heated wiper/washer system to prevent freezing of the washer fluid.

Will you get better visibility? Yes -- compared to the sealed beams, anyway. However, John Goodman reports from the UK: "Jaguar enthusiasts here actually change to the four headlamp system because of improved lighting available." Goodman isn't talking about installing four sealed beams; he's talking about installing four 5æ" round E-code units with H4 bulbs -- meaning the UK car goes from two H4 bulbs to four. If it's visibility you're after rather than the appearance of the single headlight assemblies, perhaps the easiest, cheapest and most effective improvement is to replace the sorry sealed beams with far superior E-code units using H4 halogen bulbs. These assemblies can be purchased from J. C. Whitney for less than $20 each (H4 bulb included!) and will fit right into the outer (main/dip) headlight fixture with no modifications. Higher quality units are available from Hella, Cibie, and other manufacturers.

Note that this author has purchased a set of 5æ" round H4 units from J. C. Whitney, and the lights that arrived are labelled "Maxtel™ by JF", are made in China, and have "E3" in a circle on the lens. It may be important to some to know that, while these headlights fit perfectly, their external appearance is slightly different than the original sealed beams. Where the sealed beam has a domed glass lens, the Maxtel has a "squared" lens with a shoulder that protrudes straight out of the retaining ring perhaps a quarter inch and then a very slightly domed front, nearly flat faced. It's really pretty, but if you just get two for the outer high/low positions it might not be considered an ideal match for standard sealed beams in the inner two positions.

Good solution: get four, and use the exact same lights in the inner position by using the high beam filament of the H4 bulb only. If you are the type of person to keep spare light bulbs handy, you will only need to carry one type of H4 bulb to fit all four lights. And if a low beam filament burns out, you can just trade bulbs around and use that one for a high beam only.

Note that installing a high/low unit into the high beam position (inner) will require cutting a relocated notch in the support ring behind the headlight. As you look into the hole where the headlight goes, the notch at the upper left is in the wrong place and a new one needs to be cut about a half inch clockwise. You can hold the new high/low headlight up to the fixture, fit the other two feet into the appropriate notches, and mark where you need to cut a new notch. Alternatively, you could just buy a couple new mount fixtures originally intended for the outer positions and mount them in the inners. The electrical plug will work fine as is; the two-connector plug will fit directly onto the three-connector H4 bulb and operate the correct filament.

The standard H4 bulb is 60/55W, which is a significant boost over the 35/35W main/dip sealed beam halogens (throughout this book, I endeavor to list the main beam wattage first, the low beam wattage second. The J. C. Whitney catalog often lists them the other way around). But the chief advantage of the E-code units is that they have much better focusing patterns; on low beam, you can pull the car up to a wall and see that the pattern provides a distinct cutoff to the upper left (on LHD cars), while still providing plenty of illumination down and to the right. The result is that oncoming traffic gets blinded less on low beam, despite the higher power of the H4 bulbs.

H4 bulbs produce a brilliant white light. This is a wonderful benefit, even beyond the actual light output. Having everything in front of the car lit up with white light instead of the yellowish light of conventional headlights seems to make everything clearer.

With the legalization of composite headlights in the US come the "9003" and "HB2" bulbs. These are both exactly the same as the standard H4 except that they are DOT approved. All three designations are commonly available, and replacement bulbs can be found in the local auto parts store or Wal-Mart; H4's are sometimes sold as "motorcycle" headlight bulbs, and may actually cost more than the identical 9003's right next to them.

Alternatively, you can replace the sealed high beam units (the inner units on each side, H5001) with E-code high beam assemblies that use H1 halogen bulbs. J. C. Whitney sells el cheapo H1 headlights, too, and H1 bulbs are also available anywhere that sells auto parts. Use of H1 high beams has the advantage that, since the reflectors and lenses don't need to be designed to facilitate both high and low beam operation, they can be fully optimized for truly excellent high beam operation. Stern recommends this method: "H4 high beam: Lots of midrange fill light. Dedicated high beam: Long-range throw. It's best to have both types and there's no benefit to the H4/H4 setup (except in places like Norway where pre-'79 vehicles can have up to four low beams of the world limits you to two.)" Since the only advantages of using four H4's are minor (fewer spare bulbs required, perfect appearance match), he may have a point; if you'd like more "midrange fill light", you can just upgrade the H4 bulbs (see below) rather than omitting the long-range H1's in favor of additional H4's. This also is a method of improving the low beam lighting, so using four H4's might not even be all that good an idea in Norway. Plus, you don't have to modify the notch in the support ring to install the H1's.

Stern adds that, as with anything else, you get what you pay for when buying E-code headlamps, and suggests you pony up for the Cibie or Hella units rather than the J. C. Whitney no-names. "Genuine European E-code headlamps perform much better than the knockoff items, which often have counterfeit E-marks and actually haven't been tested or approved at all."

Stern describes E-code 5æ" round units from Cibie and Hella: "The Cibie lamps are convex (dome) face lamps, like the original sealed beams. The Hella lamps are flat-faced." H4 high/low and H1 high beams are available from both companies. Stern goes on to note that the Hella H1 is truly flat-faced while the Hella H4 has an extending lip around the edge (similar to the Maxtels described above) so the two Hellas don't really match each other perfectly. "The difference in lens technique between the Hella H4 and the Hella H1 creates a difference in installed appearance between the two adjacent units. The Cibie H4 and H1 both use convex lenses of the same curvature. Whether this is of concern to you is a matter of individual taste. The Cibie H4 high/low units are equipped with city lights." The various nuances of the Cibie and Hella headlights are discussed in great detail on Stern's web site at

"Cibie has just introduced a complex-shape-reflector small-round setup with really impressive efficiency numbers. Now all they need to do is get the price down below the stratosphere (currently over $500 for a complete setup...ouch!)

"There is a potential design compromise in the Cibie lamps. The Cibie H4 weathershield can be installed in any clock position, so one must pay careful attention to putting it on such that the moulded-in word "TOP" is at the top, else risk water entrapment and shortened reflector life."

In installing E-code headlights, we have vastly improved the lighting without having significantly changed the outward appearance of the car. If you still want better visibility you can add more driving lights, but it might be a better idea to opt for non-standard H4 or H1 bulbs -- see below.

John Goodman provides a different suggestion regarding the 4-headlight arrangement: "I would prefer the outer lamps to be the permanent dipped beam units as in the BMW's, i.e. The H1 single filament bulbs, because the reflector shape is different being solely designed for dipped use only, gives a better light pattern. This arrangement needs mods to the headlamp relays so they stay on when the inner main beam units are activated." No problem; a jumper between terminals 56 and 56b on the main/dip relay will do it.

For people like Goodman wishing to retrofit the four-headlight system into a non-US car but who drive on the wrong side of the road (UK, downunder, Japan), note that you must get headlights with low beams that cutoff the upper right. The boxes the Maxtel headlights from J. C. Whitney came in indicate that they are available in either RHD or LHD versions, but J. C. Whitney apparently doesn't offer any headlights for RHD cars. I'm sure there are suppliers of suitable units in your countries, and the same type of improvements should be possible.


HEADLIGHT AIMING -- FOUR ROUND HEADLIGHT SYSTEM: Another nifty feature of having four separate headlights is that you can get creative aiming them. The outer high/low units probably should be aimed pretty much as normally specified to ensure that oncoming drivers are not blinded. If E-code units are installed, this becomes both more important and more acceptable, since the E-code lights have a very sharp cutoff indeed; a little too high and you're blinding people, a little too low and you're not lighting the road very far ahead, but just right and you get excellent visibility for low beams. Unfortunately, aiming the low beams accordingly will determine where the high beams end up, so you have limited options there. Fortunately, E-code high/low units seem to provide excellent high beam patterns when low beams are aimed properly.

The inner high beam units have more flexibility. If it is presumed that they are never on when there are cars out there that may be blinded, you can aim them pretty much whichever direction you wish. One suggestion might be to aim them slightly crosseyed, the precise amount depending on the spread pattern of the high beams themselves. With this setup, the inner units provide fill-in lighting between the outer headlights at close ranges; at medium ranges they converge to illuminate a single spot; and at long ranges they cross and spread out to illuminate the sides of the road.

If you have driving lights instead of fog lights and they are wired to come on with the high beams, you may have even more aiming possibilities. The driving lights could be aimed far crosseyed or skewed; either way, they would help illuminate the sides of the road in curves. In fact, this pattern also works with fog lights, since you aren't that concerned with distance (you won't be driving that fast in fog) but you are concerned with curbs and the like.

Of course, once again there are legal issues. Even though the high beams are only used when nobody is around but you, the US gov't still requires you to aim them the way they think they should be aimed. Again, this probably won't pose a problem in most areas; cops generally only issue tickets for poorly aimed headlights where someone is driving a car that's been crashed and one of the lights is aiming at the ground or off at 45 or some such. If you have vehicle inspections, though, headlight aiming is one of the things they typically check so you would have to aim the headlights the specified way before an inspection and put them back the way you want afterward.


US OBLONG HEADLIGHT (CARELLO) IMPROVEMENTS: Possibilities include replacing the DOT-approved Carello composite headlights with the earlier 4-headlight system and installing E-code headlights as described above, or installing the Euro-spec Cibie oblong XJ-S headlights. Both options will help visibility considerably, but neither option is legal in most of the US; converting to the 4-headlight system and using DOT-approved sealed beams is legal but will not improve visibility.

For a wattage boost (also illegal in the US), J. C. Whitney offers 9004 bulbs in 100/55W and 100/80W versions. Carello headlights are made entirely of polycarbonate, which is the same stuff compact disks are made of; the next time MSN or AOL sends you a CD-ROM, rather than throw it away you might test it to see how hard it is to melt. It's good stuff and the Carello is a pretty large housing, so it's not likely you will melt the housing using high-wattage bulbs. Note that, as of this writing, this author has received several reports of successful use of 100W bulbs in Carello headlights and no reports of melted parts, but this nevertheless must be considered a try-at-your-own-risk type of suggestion.


EUROPEAN OBLONG HEADLIGHT (CIBIE) IMPROVEMENTS: One possibility is John Goodman's suggestion for converting to the four headlight system. He describes the kit from Jaguar, JLM 10357: "All 4 lights are the same and still use the H4 bulbs. A link wire supplied with the kit only enables the outer lights on dip. Could easily be wired for both pairs on dip, but would screw up the dim/dip and not sure if it's legal. Looks like it's been done this way for simplicity of owner installation. Although it remains a mystery why the genuine Jag kit did not have dedicated driving lights for the inner pair with H1 bulbs."

"If you have converted to four headlamps, the headlamp washer/wipers are now redundant, but you can utilise the additional separate pump for the headlamp washers (modify the wiring) to power one side on your screen washers, works well." Of course, this only works if you have an '88-on car with two separate nozzles -- or have added a nozzle in addition to the original single one.

Unless you prefer the appearance of the four-headlight system or your existing headlights are damaged, you might as well keep the European oblong headlights; they have good patterns, you can get plenty of light from them -- and the wipers work on them. One of them uses H1 bulbs and the other uses H4's, either of which can be replaced with nonstandard upgrades -- see below.


BETTER H4'S: Although considered somewhat exotic in the US, H4 bulbs are perhaps the most popular light source for headlights in most other parts of the world. It should come as no surprise that there are many companies trying to make improvements on it.

One way to get better visibility is more wattage. J. C. Whitney offers H4 bulbs in 100/80W, 130/90W, and 165/100W. The 165/100W's are kinda pricey, but the others barely cost any more than standard H4's. You can even get the E-code assemblies from J. C. Whitney with the 100/80W or 130/90W's already installed for only an extra buck or two.

Also, Vince Chrzanowski reports that he found 100/55W H4's at his local electronics wholesaler: Eiko Order Code 01019-BP. Eiko products are distributed by:

Wiko, Ltd.
10490 W. 164th Pl.
Orland Park, IL 60462

And, no, he claims there is no typo, the name of the company is one letter over on the keyboard from the name of the product line.

Daniel Stern advises that "good quality European bulbs cost no more than Chaiwanese stuff from JCW or Wiko, and the wattage ratings on European bulbs are actually correct. The knockoffs are almost always quite a large bit lower than stated, never higher. This is not the case with European-made bulbs."

Note that the light output of light bulbs is not necessarily proportional to wattage; usually the higher wattages are more efficient. Suffice it to say that high-wattage H4 bulbs will definitely do the trick. On high beam the reflection from a brand-new road sign can be a little blinding. And when you flash at someone to move over, they move over!

Besides increased wattage, other H4 variations include the blue bulbs and xenons described below.

Of course, the nonstandard H4's are harder to find when one burns out -- but if you buy a spare or two, they don't take up much space in the trunk or glovebox. Or, you could just buy a normal 60/55W H4 from a local store to tide you over until you can get a new specialty bulb shipped to you.


BETTER H1'S: Many of the options available for upgrading H4 bulbs also exist for H1's. The standard H1 is 55W, but 100W versions are available in most auto parts stores and J. C. Whitney sells 100W and 130W versions. Also, read about xenon bulbs below.


HIGH WATTAGE HEADLIGHTS VS. UK-SPEC DIMMED DIP BEAMS: Regarding the UK system that operates the dipped beams at reduced voltage whenever the engine is running, John Goodman says "It gets all screwed up if you try to install non-standard brighter wattage bulbs." Regarding the kits available in the U.K. to convert to the US-style four headlight system, he says "When I converted my previous XJ-S to 4 headlights the dim system still works because all 4 lights are the same and still use the H4 bulbs. All lights have dual filament bulbs, so 4 x 55w on main beam, however only the outer ones are ever wired up for dipped beam (not sure if this is a legal reason)."

If you happen to have such a UK-spec car and don't want to convert to four headlights, one nice option is the 100/55W H4 bulb from Wiko mentioned above. Since the low beam is still 55W, same as the stock H4's, the dimmed dip feature will still work as intended.


SEALING NON-SEALED H4 HEADLIGHTS: H4 headlight assemblies are nothing resembling sealed; in fact, the back end is open enough you might consider it ventilated. To prevent moisture getting in and deteriorating the reflector, the assemblies include rubber boots that fit over the back end of the headlights. Note, however, that installing this boot will keep the assembly warmer; this doesn't normally pose a problem, but if you're using the big-wattage bulbs you might consider the tradeoffs between how hot the bulb gets and how big a problem moisture is.

Other cars, including Hondas, use rubber boots that appear remarkably similar on normal sealed beams. Perhaps one of these boots could be used when the original H4 boots are damaged or missing.


SOCKET MELTING: One possible problem with high wattage bulbs is melting of the plastic socket that plugs onto the back of the headlight. The solution to that problem is easy: remove the socket and install the spade connectors individually. One idea might be to push the spade connectors all the way through the socket and out the other side before connecting to the headlight; that way, the wires going through the socket would clearly indicate which spade connector goes to which terminal, but the plastic socket itself would remain dangling on the wires a few inches away from the headlight.


AUXILIARY LIGHTS -- MORE POWER: The fog/driving lights on your XJ-S use either H2 or H3 halogen bulbs. H2 bulbs are normally 55W and may be found in local parts stores with a little looking. For more power, 100W versions are available from J. C. Whitney.

H3 bulbs are normally 55W and can be purchased just about anywhere that sells auto parts. However, for a little more visibility, replacement 100W H3 bulbs are available everywhere, and you can get 130W versions from J. C. Whitney.


HIGH WATTAGE HEADLIGHTS -- POWER SUPPLY CONCERNS: Since watts = amps x volts and automotive bulbs are 12 volt, a 100W bulb will draw over 8 amps and a 130W bulb will draw nearly 11 amps. Four 130W high beams will draw over 43 amps, or 29 amps more than the stock sealed beams did. You might wanna consider the capability of your alternator; the later XJ-S was fitted with a 115-amp unit, but the earlier ones had 66-amp or 75-amp Lucas units -- and you've still got electronic fuel injection, windshield wipers, A/C system fans, etc., etc. to provide power for. Still, this usually doesn't present a problem, perhaps because you can't use high beams too much due to oncoming traffic, there's usually no point to using high beams in the rain when the wipers are going, and since it's cool after dark the A/C fans are always on low speed.

You also need to consider the wiring and fuses. See the suggestion for installing relays, above.


BLUE BULBS: John Elwood says, "Mine is an '86 four lamp sealed beam system. I replaced the low beams with a $30 H4 conversion kit offered by J. C. Whitney. I ditched the included bulbs and bought "Crystal Blues" from Pep Boys. Of course none of this is legal but it still looks really cool. Also much better visibility." 9004 bulbs are also available as Crystal Blues.

Emile A. DesRoches, who has the Carello headlights, says, "The bulbs I run are from Imparts ( in St. Louis, both catalog and invoices just list them as "blue bulbs." They are apparently popular in Germany, with a blue tint to the glass which makes the light produced intensely white as opposed to the conventional yellow color. I've found that the whiter light makes seeing easier particularly on back roads with little or no lighting. I've personally had good results with the #9004 55(legal)/100(not) wattage. Neither has been a problem in terms of heat or excess drain on electrical system or wiring. After a couple of months with these lights in two cats, I can testify they're far brighter and easier on the eyes than the standard yellow-colored halogen. Oddly enough the bulbs appear to have a gold tinge to them when held up to the light prior to installation. I do believe they improve the quality and quantity of light over the typical halogen application."

Daniel Stern explains the appearance of these bulbs: "This is a dichroic filter coating. A dichroic coating is defined as one that reflects one color and passes its planar opposite. That means that a blue-pass dichroic filter will reflect yellow (thereby subtracting yellow from the output spectrum) with the resultant output light being blue.

"Why did the bulb under discussion appear gold when peered at in the store? Because it had a blue-pass dichroic coating on it. This means that the color it reflects will be a shade of yellow. If the bulb is held up to a light and peered through, the blue-pass characteristic of this particular coating will be easily visible.

"The bulbs are marketed under such names as "Blue Sapphire", "Crystal Blue", "Blue Ion", "EuroBlue", etc. They are all the same."

Elwood adds, "You apparently at one time could get them in bizarre colors like green, red, and several other colors but apparently they were not such hot sellers as blue."

While citations for using E-code headlights with regular H1 or H4 bulbs in the US are almost unheard of, use of these blue bulbs can result in serious legal trouble. The package on a set of Crystal Blue 9004's in a local store says they are DOT approved in small letters on the back of the card, but clearly warns on the front that they are for show car use only and that local laws should be checked before installing. The bulbs themselves say nothing at all. Stern clarifies the legal issue in no uncertain terms: "Simply put: They are illegal in all of the US and all of Canada, Australia, Europe, Japan... Read the text of Canadian Vehicle Safety Standard #108 and #108.1. These are the headlamp specifications for on-road use in Canada. Both specifications clearly state that all light issuing from the front of a motor vehicle for illumination purposes must be white, white-to-yellow, or yellow. The analogous US Federal Motor Vehicle Safety Standard, FMVSS108, contains the same requirement. Federal Motor Vehicle Safety Standard 108, Canadian Motor Vehicle Safety Standards 108 and 108.1, and ECE Regulations 5, 6, 8, 20 and 37, all call for "white" light. A halogen or tungsten bulb that emits blue light is deemed a blue light, and is illegal on non-emergency vehicles in Europe, the US, and Canada." While using normal H4 headlights might not get the cops' attention, these bulbs are obviously and obnoxiously bluer than other headlights from a mile away so harassment from law enforcement will be constant and unceasing.

Besides the legal issues, Stern points out they're not really a good idea anyway. "The output spectrum of halogen headlamp bulbs includes very little light in the blue frequency range. These blue bulbs have a filter coating on them that allows only the blue frequencies through the filter. Because very little light is produced by a halogen bulb in this range in the first place, it is only this very small amount -- a tiny fraction of the total amount of light produced by a halogen bulb filament -- that ever reaches the road. You can confirm this with a good-quality light meter; even a very apparently-bright blue bulb actually throws very little light. This illuminates -- so to speak -- the difference between the signal image (what you see when you look at an illuminated light) and the emitted flux (what is thrown from the light to illuminate, either directly or via a reflector and/or lens, surrounding items).

"Blue is the shortest wavelength/highest frequency color of visible light, and, as such, scatters the most readily." This means there is more glare from fog, raindrops, snow, etc. with blue bulbs.

So how come the fancy HID headlights are so good, when they also appear blue? "Genuine arc-discharge headlamps run with a very purplish-white character that reminds of the color of the electronic flash on your camera (because it is the same technology). But this light is, for lack of better terms, "white with a discrete blue component". That is to say, the vast majority of the output light from an HID headlamp is a good, solid white that is closer to the white of the sun than most halogen bulbs' output spectra can reach. And, in addition, there is a separate output spectrum of blue-green to blue-violet frequencies that is a byproduct of metal-halide lamps such as the HID lamps currently used in cars. That blue-green to blue-violet frequency band is "throwaway" light in an HID headlamp.

"The blue appearance of the two kinds of lamps arise from two wholly separate phenomena. The main thing is to keep in mind that the blue signal image of an HID headlamp is a throwaway byproduct of a light source that emits a great big lot of very nice white light, while the blue signal image of a tinted (by whatever means) incandescent lamp is the meager blue output left when you've cut out all the rest of the usable light."

Stern talks about blue bulbs in more detail on his www site:


YELLOW BULBS: As mentioned above, yellow is a legal color for headlights, with some areas permitting a yellowish shade of white while others permit downright yellow. This is for good reason; Daniel Stern says, "Until the mid 1990s, headlamps in France were required to produce yellow light. This was accomplished in one of several ways: yellow headlamp lens, yellow glass balloon in front of the bulb, yellow glass balloon as part of H4 bulbs, and dichroic filter coatings on halogen bulbs. This last method was the best, since it produced the required yellow color with very little loss in absolute light intensity. Yellow glass filters caused up to a 15 percent reduction in absolute intensity. In the mid '90s (1994, if I recall correctly) the yellow-light requirement was dropped for new cars in order to bring France into line with general European Community regulations. Yellow bulbs can still be had and used on pre-'94 cars, however.

"It's not directly apparent that yellow is a magically great color for lights. It's what happens when you subtract blue from an auto lamp. Blue is the shortest wavelength and, as such, scatters the most readily. When blue light strikes water (rain, fog, snow) it scatters in all directions and makes on-road vision very difficult. Blue also is a very difficult color of light to look at if it is at all stimulates the reaction we call "glare".

"So the French figured to remove the blue from the output spectrum of their vehicles' front lamps. The opposite of blue being yellow, the result was French yellow headlamps. There haven't been any recent comparitive studies, but yellow lamps always subjectively ranked as decidedly better in poor weather and lower in glare than white ones, and this matches my own experimental experience with fog lamps and headlamps that produce yellow light.

"One problem with this conclusion as applied to headlamps in France is that the dichroic technology came along very shortly before France rescinded the yellow-light requirement. Therefore, the lamps that were being compared with white lamps were almost universally yellow by dint of earlier methods (yellow glass) which reduced the absolute intensity of the beam, which may or may not have had a large part in reducing the glare. Because the requirement for yellow light no longer exists (though such light is optional in many countries) we probably will never know the vagaries of the answer to this question. Suffice it to say that yellow light makes a better fog lamp if you intend to use the fog lamp in poor-visibility conditions without any drawback in dry conditions, and modern dichroic techniques of "yellowing" the light take away some of the drawbacks (reduced amount of light) that used to be a problem with yellow lights.

"These days there are quite a number of dichroic (yellow-pass) lighting products on the market. There are bulbs with this coating, as well as auxiliary lamps whose lenses are so treated. There's nothing the matter with doing it either way (though my preference is for the coating to be on the bulb, because this makes it easy to switch between clear/white light and yellow light as desired).

"There are two commonly available levels of dichroic-filter coating strength on auto headlamp bulbs: A light coating which "skims" the highest-frequency blues off of the output spectrum, causing a yellow-tinted white light, and a heavier coating that blocks all of the blue frequencies from being output, causing the full-depth yellow light that we used to see in French headlamps. The deeper yellow tint is more effective at cutting through obscured environments (rain, fog, snow, dust), but the lighter coated bulbs meet international definitions of "white" light for headlamps. I've done considerable experimentation with various mixes of bulbs and my own preference for maximum visibility in bad weather is:

  • Lightly-filtered headlamp bulbs to produce legally-white light that gives considerably less glareback in bad weather
  • heavily-filtered fog lamp bulbs to produce yellow light that does not glare back at all in bad weather (full-strength yellow is legal in auxiliary lights)

"I like clear bulbs in driving lamps, because if you're worried about glareback, you're not using your driving lamps!"

So if the bulbs with blue dichroic coatings appear gold when you look at the bulb itself, what do the bulbs with yellow dicroic coatings look like? "The legal-yellow ones reflect a light purple, while the full-tint ("French") yellow ones reflect a deep blue."


HIR: Howard Chu mentions another advance in headlights: "GE's HIR bulbs, which have a bulb coating that reflects infrared. This again allows visible light to escape unhindered, but keeps more heat in the bulb. The point here is that the filament glows because it's hot, so if you can keep more heat in the bulb, you can keep the filament glowing brighter with less electricity." For those of us who really don't care how much electricity our headlights use, this is of no importance whatsoever; the same legal light output limits apply regardless, so makers of HIR lights must design them to produce the same amount of light -- the only benefit is that they use less electricity. If you're willing to violate the light limits, conventional high-wattage bulbs work just fine.


XENON: It's a gas, but trying to use the word to describe a lighting type is just asking for confusion. Daniel Stern says, "In the field of lighting, a "Xenon lamp" is a gas-discharge (or High Intensity Discharge)-sourced light, just like the light source in your camera's electronic flash. And we're seeing more and more such lights (under a plethora of brand names, which makes things even more confusing) on today's cars. But, we also have some companies using "Xenon" in their trade names for halogen bulbs that have a higher percentage of Xenon in their fill gas mix." So, either type headlight could properly be called "xenon", but one has a filament and the other doesn't. The cost difference is also about a factor of 100.


"XENON" HALOGENS: Nathaniel Musselman found that Hella offers bulbs that look and work just like standard H1 or H4 bulbs except that they have xenon gas in them. They claim that the use of xenon gas improves light output and eliminates UV radiation that may damage plastic lenses and housings. Hella describes these bulbs on their web site at

Note that this site claims repeatedly that these bulbs are a plug-in upgrade, but that's because the site is in New Zealand and the guys setting it up forgot that the web is international; if the car is US-spec, they will definitely not plug in unless you have already upgraded to E-code headlights as described above.

Daniel Stern says, "The gas mix in such a bulb does have a higher percentage of Xenon, but it's not exclusively Xenon. Also, the gas mix in the new type bulbs is under higher pressure. This allows the filament to run hotter, which produces more light. It's not a knock-your-socks-off improvement, but it is certainly noticeable.

"The newest types of bulbs all use this new gas mix formulation (which also is under a higher pressure). For instance, the H7 is one of the newest headlamp bulbs. All H7 bulbs have this newly-tweaked, higher-pressure gas mix, and the results have been good, with the H7 achieving a higher luminous flux (amount of available usable light) from a given wattage (55w in this case) than was achievable in a bulb of this general type with the old gas mix under the old lower pressure. So after a few years' experience with H7s, the manufacturers have moved to update the older traditional bulb types with the new gas mix under the new, higher pressure.

"Note also that Hella does not make bulbs. They buy them from Osram and Philips and put them in yellow "Hella" boxes. Hella's US line currently excludes these Xenon bulbs, but Wagner sells their "Xenon BriteLite" line of US-type bulbs (HB1/9004, HB3/9005, HB4/9006, HB5/9007), and several reputable European makers (Osram, Philips, Jahn, Narva) make Xenon-filled European-type bulbs (H1, H3, H4--no H2s yet, and the H4s work in HB2/9003 US-spec lamps)."


HID (XENON): Gas-discharge xenon lights, such as the strobe bulb in your timing light or camera flash, work by firing an arc through a tube containing xenon gas. HID headlights work similarly by providing a continuous arc to provide a continuous light. These lights have no filament; the arc travels through the gas itself to produce the light. The same arc provides high and low beam; the arc is physically moved from one position to another by application of a magnetic field, so the light doesn't really turn on and off when switching between high and low beams but rather "moves". The HID headlight system provides a purplish light and gives more light than halogen headlights for one third the wattage.

The Sylvania web site has several interesting items on high-tech headlight systems, some of which might be applicable to the XJ-S:

Sylvania makes HID systems only for cars designed specifically for them such as the Lincoln Mark VIII, but a Sylvania rep says "we know that PIAA and KC Hilites both offer HID units for the aftermarket (we believe for off-road use), although the prices are quite high." That off-road use comment is probably a legal technicality. The note about the prices is no lie, though, HID's cost in the thousands.

John Elwood: "J. C. Whitney sells real HIDs for about $1500. I'd rather buy another MG..."

Nathaniel Musselman says you can also visit

Daniel Stern: "HID headlamps, which have a bluish appearance, are legal. It's because they're not actually blue, they just appear more blue than the halogen lamps surrounding them. They are higher in blue and blue-green wavelengths, but this is specifically noted and approved in CMVSS108 and 108.1 (And, for US readers, in FMVSS108)."

Someone named "Michael" on the online Corvette discussion list gave this description: "The HID headlamps are essentially mini versions of the lamps under which you watch your favorite team do battle at night. And, just like the stadium lights, the natural tendency of these lamps is to take minutes to warm up. So, the lamps use a bunch of sophisticated electronics to warm them up quickly and keep them operating steadily at the several-thousand (or so) volt level, all while being powered by the notoriously dirty and varying car voltage (12-14 volts). Unfortunately, these electronics and power supplys cost $, weight, and real estate. Couple that with the already deep optical path of an HID, and you are talking one big (i.e., long/deep), heavy, and expensive package. Two per car, please...

"Advantages? A much cleaner light, designed to illuminate objects in a dark environment with the strongest possible contrast. The output spectrum of these lamps has been "tuned" to just the spectrum needed for the task, and the technology goes places where no glowing metal filament has ever been. The results need to be seen from the driver's seat to be believed. Way, way, cool. The twenty-first century headlamp.

"Disadvantages? The usual suspects: Weight (big penalty), cost (massive penalty), size (tremendous penalty), electrical noise (beaucoup shielding for the lamp assy. and engine compartment is required to keep your delicate little OBD II-compliant computer happy.) This fabulous, Close-Encounters-of-the-X-Files-Kind light also has some serious potential to blind oncoming drivers and anything else. Note how many cars using these lamps have some type of suspension leveling device. The backlash has already started in Europe, where drivers are complaining about being blinded by BMW's overloaded with a trunk full of beer."


ALTERNATIVE CONTROL SCHEMES: Besides upgrading the hardware in the headlight systems, there may be benefits to changing the ways in which the headlights can be operated. It would be possible to add dozens of schemes here, each complete with wiring schematics, thereby significantly adding to the poundage of this book. Rather than going that route, I have decided to merely put forth some of the more intriguing ideas that have occurred to me or have been sent to me, and leave it to the owner to figure out how to implement them if he so desires. Basically, any of them can be achieved with a switch or two, a couple of relays, and a couple hours of fiddling with the wiring.

John Napoli suggests rewiring the car so that the low beams remain on when the high beams are on, so all the filaments are putting out light. The early European headlamps with two H1 bulbs did this from the factory, and show how easy the rewiring is -- simply adding a jumper between terminals 56 and 56b on the main/dip relay. However, perhaps it should be noted that those early cars had separate bulbs for high and low beams, while later cars have both filaments within the same bulb. Overheating or early bulb failure might be the result. Hence, try this modification at your own risk.

If you have the 4-headlight system, Daniel Stern suggests you can go nuts with control schemes: "In a quad-round system, there are four holes and six filaments. Nobody ever said you have to have two matching pairs of lamps, or that you can't rewire the setup to create 3 beam distributions rather than just two (or even five if you're adventurous)." Just as an illustration, one of Stern's alternative setups is to provide three levels of light: standard low and high beams, plus a "mid beam" arrangement with the outer headlights on high beam but the inner headlights off. This setup makes good sense if the inner high beams are an H1 assembly with really long-range capability, and it only requires one switch and a relay. Using all four high beams will provide truly excellent visibility while you are alone on the road but the H1's can be turned off to avoid blinding another driver you are following at a distance while still keeping the outer headlights on high beam to provide good visibility at closer ranges. And since you have switched from four headlights to two, that guy thinks you have switched to low beam already and doesn't get mad at you for blinding him.

Some alternative control schemes involve the fog lights or driving lights, whichever is fitted. To see in fog, it is essential that the fog lights be the only lights on; main or low beams just cause glare. One idea for convenient fog light operation is to rewire the car so that you can put the headlight switch in one position and use the stalk switch to flick back and forth between low beams with fog lights and fog lights only. That way, when you come out of the fog bank, you can just flick the stalk to bring on the low beams for better visibility in clear air, and just as easily turn them back off when you encounter the next patch of fog. There's really no need to be able to get to high beams without putting the master lighting switch in another position, since whenever there's fog around you won't be driving fast enough to need high beams.

Note that you might need to check local laws here. At one time, it was illegal in some states to drive at night with fog lights only, fog or not. Hopefully, more rational legislators have repealed such laws... what am I saying? There's no such thing as rationality in legislation, or the stupid laws wouldn't have been written in the first place! Maybe you can get by with a set of pilot lights; maybe the cops are stupid enough to think the headlights are "on" -- at least long enough for you to get past.

If the car is fitted with driving lights instead of fog lights, it might make sense to rewire the XJ-S so that all the headlights and driving lights work at once. In fact, later US-spec XJ-S's came with a master lighting switch with an additional position that operates all six lights. It may be possible to retrofit this switch into the earlier cars. Or, you can simply defeat the "inhibit relay" in these earlier cars, allowing high beams and driving lights to be used simultaneously; it might also be a good idea to add relays to prevent overloading any circuits.

With the options available for improving the headlights, there really is little reason to operate the driving lights simultaneously to get more light; you should be able to get plenty of light from the main beams. However, the driving lights might make excellent "cornering lights" if you aim them towards the sides of the road.

In many states, there once were 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!). The owner is advised to check his state's current regulations before rewiring for all six headlights to operate at once.

If your desired wiring scheme requires another switch, John Goodman points out that the UK cars have a different headlight switch which can be pushed in to turn on "fog lights" at the rear of the car; this push facility could be used for whatever your little heart desires, leaving your dash uncluttered with additional switches.


PILOT LIGHTS/CITY LIGHTS/PARKING LIGHTS/WHATEVER: As mentioned in the secion on Electrical, non-North American cars typically use low-wattage white bulbs within the headlights as markers, while cars in the US typically use the dimmer of two filaments within the front turn signals. However, according to Daniel Stern, "Note that city lights are a legal form of parking lamp in the USA and Canada. Parking lamps can be amber or white, and they are permitted to be nested with the headlamps. The latest XJ sedans use city lights rather than amber parking lamps."

This, of course, suggests an interesting possibility for modification of US-spec cars: disconnect the parking light filaments in the front turn signal housings and wire up pilot lights in the headlights instead. If you are replacing four round headlights with E-code units, you might select units such as the Cibies that include pilot lights. Or you can replace the whole assembly with the Cibie oblong headlights that have pilot lights. If you're that kind of guy, just drill a big hole in the side of the cheap J. C. Whitney H4 headlights and tape a little bulb into it.

Stern offers several advantages of city lights over the US-style parking lights: "If a headlamp ever malfunctions, oncoming traffic still sees you as a double-track vehicle. Plus, it makes your front turn signals much clearer because they now go "bright-off-bright-off" instead of "bright-dim-bright-dim" when the lights are on. Yep, another aspect of lighting that the Europeans got right and we didn't. City lights are especially useful if you have fog lamps. On foggy days, you can put on the city lights which will show other drivers very clearly where your car is, and switch on the fog lamps so you can see.



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