CJ: need electrical help with new tail lights

[daniel_buck]

So my 'new' willys had some big square tail lights (just like modern TJ tail lights) and not liking how they looked I picked up a set of round LED tail lights that I think look much better.

However, I'm an electrical idiot. I always seem to mess up when it comes to electrical things, hah! And this time is no exception :-D

So the tail lights that were on the jeep used 3 wires. Red, Black, and White. And the wires on my new tail lights are also Red, Black, and White. The instructions state:

Black - Brake / Tail
Red - Turn
White - Ground


I put the lights on quick-connect male/female connectors (so they can be easilly removed, or switched around!) and connected them up to the same color wires. Well apparently that doesn't work.

With the lights turned off, I get no blinkers or brake lights. No light at all. With the lights turned on, all I get is blinkers. No constant light or brake light.

I DO have a volt meter with a bunch of different modes, but I honestly don't know where to start. Can anyone give me some advice? Anyone who lives near me willing to swing by (or I can drive to you, if it's not far) to give me a hand? I'm guessing for someone who knows electrical stuff, this is probably going to be super easy, hah!

Oh and yes, the old tail lights worked perfectly.

[jonah]

Hey there! It would be super easy to show you in person. Basically you need to put the meter on the DC setting. Then turn on each light one at a time and test the jeeps harness with the meter to figure out the correct wires for each light. Then connect according the tail light diagram. I ran my ground right to the frame near the tail light, I doubt if the harness ran a ground to the back of the jeep so you will probably do the same. You may also have to switch out the blinker relay to a LED compatible one, although it sounds like yours might be working. Also, usually the turn and brake are on the same circuit of the light, are you sure the instructions say:
Black - Brake / Tail
Red - Turn?

[daniel_buck]

Thanks, that sounds easy enough! And how do I check for ground? I guess it would be whatever wire doesn't get a meter reading, eh?

Yes, you read correctly. Turn is a separate wire from brake.

These tail lights don't have a reverse light, but there wasn't even a bulb in the spot where the reverse light was on the old tail lights, so I guess if I wanted a reverse light I'd need to run a new wire back there and pick up a little reverse light? I'm probably going to want to do this, because this jeep will see alot of time in-town.

[jonah]

There probably isn't a wire for the ground. Most likely the ground for the old light was through the housing where it was bolted to the body. On the new light with the ground wire you can just screw it to the frame or body.

First figure out what you have in the harness then we can figure it out from there. Sometime the wiring can get strange on the old jeeps depending on who worked on it before

[jonah]

The wires you have in the harness are probably: tail light, brake/turn and reverse.

[daniel_buck]

I'll give the volt meter a try tonight, see what I come up with. Thanks Jonah!

And yes, the tail light is bolted directly to the metal body.


Oh yea, one wire might be reverse, I didn't think about that. I'll look at the old tail lights and see if there's a wire going up to the reverse bulb socket.

[daniel_buck]

Yep, indeed, the red wire on the old tail lights was the reverse. The black and white went directly to the main bulb. So I'll just double back the ground wire on the new lights to the stud that holds the tail light in place, since that's bolted through the sheet metal. That a good idea? Or better to not mount it to the light itself, but elsewhere? There's plenty of bolts back there for me to sandwich the wire connector into.

[jonah]

Ok, so the black and white: one will be tail lights and the other will be the brake/turn. Then the whole circuit was grounded through the old housing. So on the new lights you will ground the white to the body or frame. Then hook up the tail light wire from your jeep to the black on the new light and the brake/turn wire from the jeep to the red on the new light. Then add a reverse light!

[daniel_buck]

And it looks like I won't need to run new wires for the reverse light(s), haha, nice! Ok, I'm all packed up for my trip this weekend, so I've got some time to fiddle with the lights again!

[jonah]

Alright, Good Luck!

[daniel_buck]

Yep yep, thanks Jonah, it's working now! When I get back from this weekend's trip, I'll pick up a reverse light. That will just need two wires, correct? The existing reverse wire, and a ground?

[jonah]

Yes, the reverse lead from the harness and then ground the light to the body/frame and you will be good to go...backwards