Brake light mystery

[Mark1972]

Good day all. Still in reassembly mode with the '70, and have a left, or driver's side tail light issue. Here's the problem. All the rear lights work on the car as they are supposed to except the left brake and signal light. The left works on hazard, and the whole passenger side works fine. The left side uses a mix of green and black wires, the right using the black and brown wires. I've checked continuity of the green wire from the plug near the parking brake all the way to the left tail light, and it's good. No broken wires. Last year, while driving the car to storage, the left brake light would flicker on and off, and now nothing I can do makes the bulbs light up. Fuses good. Bulbs good. Any thoughts would be much appreciated. Driving me crazy.

Mark

 

[BeepBeepRR]

Grounding.. always check to make sure they are grounded good.

 

[PurpleBeeper]

Yep, grounds. I had to run an extra ground wire soldered to all my bulb sockets. Grab a long wire & connect it to negative of battery (or other good ground) & touch that wire to the socket/edge of bulb for the lights in question....if we're right, they should light up....with flashers or brakes or whatever on of course.

If not that, then I guess the problem would be in your wiring and/or turn signal switch that ends at that kick panel plug you mentioned (since you know the wires from there to the bulbs are good)

 

[Mark1972]

Ran the wire from the negative battery terminal directly to the bulb socket. Nothing. Tried both bulb sockets. Not even a flicker. Also checked the continuity on both sides of the plug at the kick panel plug, and there is no issue with the connection. So if I had a perfect ground and nothing, then that means there is no power correct?

 

[Gold Rush]

If I were a betting person the turn signal switch would be high on the suspect list. I imagine they are pretty much the same as my '74 so I'll include a page from the FSM. Hope it helps.

 

[Sixpactogo]

I would look into the turn signal wiring in the steering wheel as a primary suspect. I had an issue with mine once that the signal light was not being cancelled properly and when ever I turned left the turn signal canceler was not moving the arm all the way. It would cancel the signal light but then I would not have a brake light on the left side. Same issue with the right brake light after turning right. Long story short, The brake light and hazard functions go through the turn signal mechanism. If there is a continuity problem in the turn signal switch you will have those kinds of problems.

 

[Mark1972]

Well that probably explains it then. Last year, while driving the car to storage I turned left at an intersection and the my left brake light went out. Left signal still worked. I actually have an original wiring diagram for the car, which I am teaching myself to understand, lol. There seems to be a lot of info on the forums for doing this.

 

[Mark1972]

Just an update. Pulled out the turn signal switch. I was surprised at how easily everything came apart, which is a nice change from most things. Anyway, I'm not sure if it means anything or not, but I could find no broken or corroded wires, and no broken or cracked plastic. All in all, it seems in ok shape. I also did continuity tests on the wires from the plug to the corresponding attachment on the switch itself, and everything was good. My knowledge of electrical is pretty poor, so I have to ask, is there something that could still be wrong with the turn signal switch even though there appears to be nothing broken, loose, or corroded?

 

[Sixpactogo]

Well that probably explains it then. Last year, while driving the car to storage I turned left at an intersection and the my left brake light went out. Left signal still worked. I actually have an original wiring diagram for the car, which I am teaching myself to understand, lol. There seems to be a lot of info on the forums for doing this.

I was thinking about your issue. Mine was exactly the same. What I found to be the problem was that when I restored my steering column, I painted all the components. In doing so, I sprayed some paint in the recess that the signal arm mounts into. That paint was what was not letting the turn signal arm return to center. Once I cleaned the paint out of there, my problem went away. Maybe your problem is the same.

 

[Gold Rush]

I was thinking about your issue. Mine was exactly the same. What I found to be the problem was that when I restored my steering column, I painted all the components. In doing so, I sprayed some paint in the recess that the signal arm mounts into. That paint was what was not letting the turn signal arm return to center. Once I cleaned the paint out of there, my problem went away. Maybe your problem is the same.

Did you also continuity check the turn signal and emergency flasher switches? If you find some not reliable try spraying a little silicone spray on them and working them. Be VERY careful using contact cleaners on old plastic. They often do not play well together.

 

[miller]

Whether you have the turn signal switch installed, or not. Do an ohms test on that wire, with the switch in that turn position, to see if it's making good contact. You might have to trace it all the way to the power source.

 

[moparlee]

I recently went through this on my '71 Challenger over on the FEBO site and just fixed the problem yesterday. All my head lights, tail lights, parking lights and signal lights worked except for the brake lights. Traced it to one of the wires on the turn signal switch which was not making good contact at the rivet connection. When I wiggled the wire the brake lights would work intermittently. Lightly peened the connection and all is good. I did not remove the TSS from the steering column and was very happy to save the factory switch.

 

[Mike Szadaj]

You checked for continuity, but it could also be a short. I found my passenger tail light wire was shorted to the black common wire that is part of the wiring harness. Even if shorted, the continuity test will still show good.

 

[Mark1972]

Thanks all. I have ordered the new switch and it will be here tomorrow. I checked all connections and did the wiggle the wire test at the connection points at the switch, and could not make anything light up. I'm really hoping the switch itself is the issue. I should know by Wednesday night and will update then.

 

[Mark1972]

Well, the new switch didn't do anything. I just installed it and hooked up the battery and once again, the hazard lights come on, but brake and signal on left side dead. I'm going to look more into what you had said Mike. Regarding the black wire shorting out. It's frustrating because after 6 years of restoration this brake/signal light is the only thing stopping me from driving the car, and summer here is going away fast.