foreveryoung001

Bought this '96 Xj 4.0 auto a few months ago. I've got a build thread going for all the rust repair I'm doing, but now have a situation that I can't wrap my head around.... why? Because its electrical and my brain doesn't like thinking about that stuff in logical terms.

So, when I bought it, in the middle of winter, the turn signals all worked fine. Then, as it started to get warmer, I noticed that on the warmer days, the driver side rear turn signal wouldn't flash, causing all the rest on the left side to do the fast flash dance. Then when it got cold again, say below freezing, they would work again. My first thought was a bad ground in the back area, but after taking the DMM to it, I found that it is getting current all the way to the socket, and with the bulb removed, if I touch the probes to the the contact in the center and the side, the current bounces up and down, just like it should. I've replaced the bulb a couple of different times, but am still having this issue. And now that it is always above freezing, the rear drivers side turn signal doesn't ever work.

Then today... and I'm not sure if its related, or maybe just a distant cousin, I got pulled over for no brake light on the driver side, and was given 10 days to fix it. Fine... must be the bulb... went to the Auto Zone which is right next to my work, and bought some bulbs.

When I switched them out, the new one wouldn't work when it was put in the correct way. If I put it in backwards, one of the filaments would light up... I'm assuming because it was grounding on the side, where the running light would ground, but doesn't really matter because it wouldn't lock in anyways, being backwards.

Took the DMM to it, and with the break light pushed, I get current (I was in the AZ parking lot, so forgive me for not remembering what the reading was) and when the brake pedal is released, I get no current. Then, after messing with for a few minutes, and getting the help of one of the Auto Zone guys, we got it working.

Thanked him, drove off to grab some lunch, and figured I'd double check that it was working when I got to the sandwich shop... NOPE!

DAMN!!!!!

Grabbed something to eat, then checked it again when I got back to work... and low and behold... the brake light works again! WTF!?

So I am at a loss as to where to look for the culprit. I can run to the local JY in the morning and grab new (Used) sockets for the turn signal and brake light, and solder them in, but is that where my problems lie? Or does this sound like a wiring problem further up?

Since I'm getting readings on the DMM at the socket, I'm thinking it must be something in how the bulbs are seating in there, but again, my brain doesn't look at the electronic issues with the same clarity as the mechanic stuff. So any help and or thoughts would be appreciated.

foreveryoung001

Had a few minutes at work here, so ran out to the parking lot to try to get actual numbers on the readings from DMM, and wouldn't you know it, the brake light has stopped working again.

Anyways, here's the readings, with break pedal pushed, from the center pin with the black wire, to the center pin from the blue wire, I get 12 volts. From the Black wire to the side of the socket (white wire... ground?) I get twelve volts.

With break pedal off, there is zero volts on all.

With brake pedal off, and running lights on, I get 12 volts from blue wire to side(white wire).

As far as my brain can figure, that all sounds right.

There are definite grooves on the bottom of the new bulb where it is making contact with both center pins in the socket.

So, once again, from what I can see, everything should be working.

Should I spend the couple bucks at the junk yard and switch that socket out?

I'm not so worried about the turn signal, although that has been driving me nuts for a while, but I have to get the brake lights figured out so I can take care of my fit-it ticket.

Kingfisher

Most weird light problems are caused by bad grounds.

foreveryoung001

Just ran out and checked the ohms from the ground wire on the socket to the body of the jeep and I'm not getting any reading, which if my limited understanding of electronics is correct, it means there is no continuity on the ground wire.

So, rather than dig though the body of the jeep to find the current ground, could I just splice in to the ground wire on the socket and add another fresh ground to the body?

In my head it seems like that solution would work... but my head isn't always right. LOL

Kingfisher

Sure

foreveryoung001

Well... that didn't work. After work, I grabbed a loose wire and spliced in to the wire from the socket, grounded it on the frame. Still get the same readings on the DMM, and the running light part of the bulb lights, and the brake light still doesn't.

For good measure, I pulled the other side off and checked the readings on the right side, so I had something to compare it to, and I'm getting the same readings (within a few decimal points) as the left side.

With break pedal pushed:
Left side: 12.9 volts
Right side: 12.4 volts

The grounds on both sides are ohming out close to the same

but the right side work and the left doesn't.

The inside of the socket was pretty clean, but took a wire brush to it, just in case, but that didn't change any of the reading or fix the problem.

So, the next thing, I'm thinking, is changing out the socket with one from the junk yard. The only thing I can reason, in my head, is that something must be losing contact when the bulb is pushed down and twisted to lock it in.

I guess I will run down there in the morning, grab one for the brake/running light and one for the turn signal, and see if that solves the problem.

They're only going to be a couple of bucks, but I still hate throwing money at something when I'm not positive what the problem is.

I think I need a beer! Things always seem easier to deal with when beer is involved.

freegdr

If there grooves in the bulb contacts replace them where Id start .

foreveryoung001

Well, opened everything up, found two grounds. One for the regular lights and one that was added for the trailer lights. Refreshed both of them, going down to bare metal, but it didn't fix anything.

So, I had picked up two sockets yesterday morning at the junk yard. One for the brakes and one for the turn signal, and spliced those in, and the turn signal started working, but the brakes were still a no-go.

Grabbed the DMM and started testing the plug that is up inside the body, and as I was moving that around, poof! Brakes come on. Wiggle the plug some more, and brakes go off. So, opened that plug up, and scraped all the contacts clean. Put it back together and everything is now working!

So, turns out I had two separate issues. The socket for the turn signal and a dirty plug for the brakes.

Thanks everyone for all the suggestions. If I hadn't have opened up that back panel to search for the grounds, I don't think I ever would have noticed that plug. It was hiding way back there.

Tejasol

I have the same exact issue with my 87. Where exactly did you find the plug inside the body?

foreveryoung001

It was behind the drivers side tail light. If you follow the wires backwards from the sockets, they all come together as a single bundle, and if you follow that towards the front of the vehicle, you'll find it.

On the plug, it had one of the those plastic holders, like it was anchored to the frame at one point, but mine was pushed up and hidden, which is why I never saw it. I think the guy that did the trailer wiring did a bit of a hack job. Getting it apart was the hardest part, cuz I had to reach up through the hole that the wires come through for the taillight and then reach through a hole under the plastic, behind the spare tire, right by where I found the ground connection. If they had made the wires about 4 inches longer, I could have pulled the whole thing out the back and been able to see what I was doing. Stupid engineers!

I didn't get any pictures of mine, but here's one I found online. Looks like it might be easier to access from the side.

Tejasol

OK, thank you very much!

I've replaced bulbs, brake switch and checked a couple of grounds. I will check this tomorrow.