H4 Conversion Headlights Installation
1991-1993 3000GT/Stealth
This page was originally created by Joel Kelly. All text and pictures were done by him, and is used on 3SX.com with his written permission.
* * NOTE: There is an addendum at the bottom pertaining to the H4 harness currently sold through 3SX.* *
A disadvantage of earlier model Stealths is that they use sealed beam headlights. This makes it difficult and expensive to replace the lights as they age or to upgrade them to something better. 3SX Performance sells several conversion kits to allow 1st generation cars to use the stardardized H4/9003 bulb. One of the conversions they sell also mounts a projector lens in front of the bulb. Projector headlights generally have a sharper light cutoff than conventional reflector lights. This headlight conversion is not a true projector, but more of a projector/reflector hybrid. There is a reflective backing behind the bulb that also throws light ahead of the car. It probably would have been possible to engineer the backing to direct all light towards the projector lens, but the costs involved in this would have made it unmarketable.
These are the headlight housings and rubber boot that was included. You can clearly see the projector lens and the reflector behind it. Compared to the stock headlights, these look very different.
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Assembling the headlight was straightforward. I purchased a set of Sylvania Silverstar 4000K bulbs and an H4 harness to splice into my existing wiring harness.
On the back of each housing is a clamp and a hole for the bulb.
After inserting the bulb, the clamp fits tightly over it. The boot can then be fitted over it, followed by the harness plug.
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The bulb is visible, though distorted through the lens.
Now to actually install them in the car. Getting to the light is a little bit involved, but it can be done with only a screwdriver. In this illustration, parts 1, 2, and 3 must be removed to allow access to the actual headlight.
Removing the upper bezel requires removing 5 screws, 1 on each side, then 2 on the front face, plus a plastic retaining clip on the inside face.
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The bezel doesn't actually have to removed, it can simply be lowered to allow access to the screws holding on the lower bezel.
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The lower bezel can be rotated forward and removed.
Remove the four screws holding the silver headlight retainer on, and then the headlight is free to move.
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Pull the plug on the back of the headlight, and you'll be left with the harness and the headlight holder.
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The stock harness obviously does not fit an H4 bulb, and must be modified. The stock wiring harness voltage is arranged as below with respect to battery ground. Note that the headlight switch controls which filamtent lights by sinking the light. This means that two of the leads will always have power while the ground is switched to trigger each light. The H4 harness is connected to the stock harness as described in the table.
| H4 Harness | Stock Harness | Low Beam Voltage | High Beam Voltage |
| Red | Red | 12V | 0V |
| Black | Red/Blue | 12V | 12V |
| Green | Red/White | 0V | 12V |
* NOTE: See addendum at bottom for alternate wiring.
The bulb itself is wired as shown below. The low beam filament has a shield over it, while the high beam does not. On the harness that I bought, the wires were Red, Black, and Green. Others may be different.
The harnesses ended up being connected like so.
* NOTE: See addendum at bottom for alternate wiring.
I chose to use a four-port Molex connector to ensure a good connection and make the harness easy to remove if needed. I ended up having to lash the connectors together to be sure they would not rattle apart, but the connection is good.
Because these are projector headlights, they must be mounted inversely to standard reflector lights, with the low beam filament shield on the bottom of the bulb. This shows the ray pattern in this case. It creates a sharp cutoff point in the beam, above which very little light escapes. This is not perfect of course, and the fact that the reflector is much larger than the lens will result in some light above this point, but most of it is thrown low on the road.
Reassembling is the opposite of disassembly. Just be careful to seat the headlight securely before tightening down its retainer. Also, coil the harness in a spot where it will not be caught when the headlight retracts. I chose to tuck them on the outside edge of the light.
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The new headlights have a more anthropomorphic look to them, almost as though the car were staring at you.
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The next thing to do was aim the headlights. This is as simple as finding a good garage door and turning the aiming screws above and on the outside edge of the light. I adjusted mine so that the left low beam would fall right under the window line of a standard car, with the right one slightly higher more outward. At the end of it, I had a fairly crisp cutoff line for my low beams that should not blind any oncoming cars. There is still some glare that I could not eliminate, but it is not severe. The high beams are full-on illumination, and have no such cutoff. This is after adjustment, showing the low beams on the left, and high beams on the right.
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And the snake eyes, just for comparison.
The real test though was brightness. The Silverstars are considerably brighter than the stock bulbs, and have a much higher color temperature. A comparison of stock vs the new lights, both on low beams. Stock lighting is on the left.
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And high beams, again with stock on the left.
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And a comparison of the snake eyes, with stock on the left.
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The beam pattern from the projector/reflector combination is unique. It produces more glare than a true projector setup, but overall, I'm satisfied with it. The conversion allows me a much wider variety of bulbs, or even HID lights in the future.
Wiring Addendum - 3SX Edition
Over the years we have offered the H4 conversion housing and wiring harness adapters, we have carried 3 different versions of the harnesses with different colored wiring. The above writeup was done covering an earlier version with different wire colors. Below yoiu will find the updated colors based on testing the stock harness bulb plug with a test light, stock 92 service wiring manual, and a doagram of the low/hi/grnd plugs for an H4 bulb.
| H4 Harness | Stock Harness | Low Beam Voltage | High Beam Voltage | H4 HID Bulb | |
| Low Beam | White (or Yellow) | Red | 12V | 0V | Black Single |
| Ground | Black | Red/Blue | 12V | 12V | Black Double |
| High Beam | Red (or Blue) | Red/White | 0V | 12V | Red |
The kit is ultimately for a car that originally has H4 bulbs, either a 2-bulb or 4-bulb setup. NEITHER of which is a 3S - our cars don't have H4 bulbs, so however you choose to use the harness kit will require splicing wires. And the kit is ultimately designed to connect the headlights directly to the battery, using a couple relays that trigger when you turn on your headlights so the power going to the bulbs is coming directly from the battery using heavier gauge cable, since people typically install higher wattage bulbs (Note: I have been running 90/130 or 90/100 watters for the 12 years I've had my H4 conversion in my car using *stock* wiring with no issues, and I leave my headlights on all the time running snake eyes).
The plugs on the harness are pretty simple. The 2 brown wires tailing from the 2 red wires go to the battery. The 3-male plug has to be spliced into the stock headlight plug on the passenger side. Best I can tell, red=hi, white=lo, black=ground/common. So updating the chart on our site white-to-red, black-to-red/blue, red-to-red/white. Plug in the two relays. Plug in the H4 bulbs into the plug with all three wires (blue/yellow/black). Ground the black wire to chassis. Run the length of wire over to the passenger side and do the same. The previous is for actually using the harness to draw power from the battery. If you want to use the stock wiring, not run the power from the battery, all you need is the 2 3-female plugs with the blue/yellow/black wires. Splice them into the factory wiring: blue=hi, yellow=low, black=ground/common. So again updating the diagram on the site: blue-to-red, yellow-to-red/white, black-to-red/blue.
NOTE: When you are using the H4 HID kits sold through 3SX, you actually do NOT need the H4 adapter harness since the wiring on the HID bulbs are bare pigtails that can plug directly into the stock bulb harness:
Stock Red+Blue wire __ goes to Single Black on H4 HID Bulb
Stock Red wire / goes to Double Black on H4 HID Bulb
Stock Red+White wire \ goes to Red on H4 HID Bulb
_/ \ is the shape of the stock harness looking at where the bulb/wires plug in