They plug in but they don’t work because of the different functions. The factory setup is a 3-wire tail light:
Parking lamp power
Brake/turn signal lamp power
Back-Up lamp power
Ground through the mounting bolts.
The euros are a 4-wire light:
Parking lamp power
Brake lamp power
Turn signal power
Back-Up lamp power
Ground through the mounting bolts.
The way the factory USA setup works from the factory is that the brake light power from the brake light switch runs through the turn signal switch in the steering column. That switch normally lets the brake light power pass through and run out to the tail lamps on the brake/turn signal wire. When the turn signal switch is in turn mode (L or R), it cuts off the brake lamp power to the side you’re turning, and instead feeds that brake lamp blinking turn signal power from the turn signal flasher in the fuse box.
I will explain what to do to run the euros but before I do that, I’ll list a few reasons why you might ditch the project or at least what you might consider implementing if you follow through with this swap:
- The euro tail lamps do not have red side markers. I don’t know if inspectors in your area care, but DOT standards require red reflective side markers that are illuminated by the parking lamp circuit at night. The Euros don’t have that because the euro YJs either have a different separate fixture, or they don’t have rear side markers. I don’t recall. To keep yours officially Street legal, you might consider picking up a red rear side marker housing from an 81 and earlier CJ7. They used to have a red version of the front amber side marker mounted behind the rear tires. You could drill a 1” hole or whatever it needs, and screw it down and then be street legal.
- The euro YJs had a real rear bumper with a center license plate mount, much like a truck in today’s world. As such, the tail lights don’t have that window at the bottom to illuminate the license plate. You might want to relocate your plate to the spare tire or something and put a light on it.
- The euro tail lights are not very bright. The bulbs having those tiny windows really makes for them being quite dull. I love amber turn signals and I’d like to do the same project but when I did my testing, I was not satisfied with the output. Even using bright LEDs I like to use it wasn’t good enough for my standards.
- This will screw up your trailer wiring if you want to tow. The proper fix would be to get a 3-wire to 2-wire trailer converter to take the newly separated tail/brake/turn circuits and will combine the brake and turn portions again for a trailer. Would be a decent amount of wiring you’d need to do in the wheel wells to have a nice clean 4-pin trailer pigtail coming out that you could tow a trailer with.
Those are the negatives. If you have solutions and want to proceed, then there are only a few things to get the lights working themselves.
First, you need a constant brake input. You have a 1991 which does not have the factory third brake light. That makes the job a bit more time consuming than it would have been on a 94+ with the third brake light. You’ll need to find the brake light switch and splice into the wiring after that switch (before the wiring goes to the turn signal switch). You’d need to cut that wire and then splice onto the portion coming from the brake switch and run that power to both tail lamps on the brake circuit. You can run it down the tub harness, splice it into two wires, run the L one to the left light and terminate to a weather pack terminal that you can insert into the factory 3-wire body side tail light plug. Just put it in the spot that corresponds with brake lights on the new euro lights. Run the other leg to the right side and do the same thing. Both lights will light up when you hit the brakes and they’ll no longer be disturbed.
Cutting that brake light wire to splice onto it for the brakes actually fixes the turn signal problem too. At this point the brake power no longer runs through the turn signal switch since you cut it; which means the original factory turn signal/brake wires are now just turn signal wires. Make sure those wires in the tail light plugs correspond to the turn signal power in the euro lights and you’ll be good to go.
For the record, I love the idea of this swap and I really wanted to do it. What killed me were the negatives. What someone needs to do is a company like Quadratec or similar who sells the LED tail lights needs to make a custom light that has an amber section and an additional wire. If quadratec sold their red LED tail lights with 4 of the 16 diodes being amber, I’d jump all over it. They could still illuminate the plate properly, could still have the side marker, you’d just have to deal with the install quirks like the wiring, and then the trailer wiring if that matters. Would be awesomely bright to being a properly designed LED fixture. Unfortunately at this point the only options are the bulbs and lens housing like you bought and I just wasn’t happy with the brightness or the lack of side marker and plate light, so I ultimately settled on Quadratec LED tail lights and called it done. They are super bright as least but they certainly are not as cool as an option with amber would have been.
Good luck.