[cpistorius]

Hey guys, just bought a 84 CJ7. My issue is that I have put all new taillight/backup light bulbs in but I can't get my tailights to work.

With the headlights off, my brake lights work, but the brake lights also come on when I go into reverse, the reverse lights are not turning on. I have no tailights regardless of the headlights being on or not.

Anybody seen anything like this? All of my other electerical seems fine.

Thanks for the help.

[John Strenk]

Sounds like you have a grounding problem.

[Gummo]

I had a similar problem. The PO had spliced together the tail light and brake light wires. It wasn't easy to figure out where they were spliced.

[brian613]

wires crossed and possibly a ground issue also

[3logbridge]

PO of my yj installed a single contact bulb into a double contact socket on the tail light. After nearly loosing it, i found this. It caused my dash lights to come on when pressing brake pedal, and all other kinds of freaky stuff to happen with the lights.

[WayneMeuir]

I just completely redid the back of my 80 CJ5 becasue one of the PO's hacked it all up. Its really is not that hard, time consuming, but not hard. I used all solder connections and shrink sleeving. First unplug the connection that is near the parking brake that goes to the back and then run a wire direct from the battery to that plug so that you can verify whether you have continuity in the harness that goes to the left tail light. It all terminates underneath just behind the left rear tire. There will be three wires going across the rear of the vehicle to the right tail light, one is the running lights, one is the back up lights and one is the turn/brake lights. Ground for both tail lights is a direct ground where the lights bolt to the body You will also have three wires coming off the left tail light for same functions.
It took a few hours and I used a trailer harness flat 4 way plug to hook it back up so that I could simply unplug it instead of having to cut the solder joints. Tied it all up nice and neat after I was done and put it inside an old radiator hose that I had split down the side and tie wrapped it up in the cavity just below the left tail light, out of the way, so there is no way it will get dragged off by anything. Very little of the wire is even exposed.
Assuming your stock harness is not all hacked up, you could use a wiring diagram to see which wire goes to which function. Mine was hacked up so badly and there were so many splices, that the colors codes were all messed up, so it was easier to just cut out all of the crap splices and trace it will a circuit tester.

Wayne

Wayne

[Mike Romain]

Here is a link to the FSM that has the wiring schematics in it. Your wiring is messed up, someone has done it wrong by the sounds of it. 84-86 Factory Service Manual... - JeepForum.com

The brake and signal light 'filaments' ground through the fixture bolts. Brush guards are good for messing up this connection.

The running lights have a wire for a ground that hooks onto the tub at the back. Maybe this isn't connected or has a ratty connection?

The reverse lights are their own power line and use the fixture bolts for ground.

[cpistorius]

Cool - thanks!

[John Strenk]

I like radiator hose idea to protect the plug and harness.

if he running light ( side marker light) lost it's ground the light wold just go dead and have no effect on the rest of the tail light circuit. Good thought on the light protector also screwing up he ground. I think later model CJ's had the side lights on the tail light itself so those would ground the same as the rest of the lights.

Are you sure it's the brake lights that are comming on with the reverse lights and not the tail lights? If it was the ail lights, I could see it happening because the tail lights light up at a lower current than the brake lights.

When trying to trouble shoot one tail light at a time it's best to disconnect all other lights as any one could indicate a ground even if i's a poor one.