Some Electrical Tip

[newsome311]

I have a newly acquired '76 and trying to trouble shoot a light issue. All the other lighting on the truck seems to be in order, but when I press the brakes the driver side break doesn't come on, and the front passenger turn signal comes on. I was just seeing if anyone had some advice on how they would determine where the issue is.

Thanks

 

[Rustytruck]

check the grounds at the tail light buckets and the ground screw at the rear frame on the drivers side close to the bumper.

 

[B RON CO]

Hi, X2 on the grounds, the grounds are usually corroded. Don't assume the bulb is good. Check the leads in the socket for power with a test light. Most of us have some extra 1157 bulbs laying around. Good luck

 

[EPB72]

What they said grounds /contacts in sockets and socket body itself thats the bulb ground...

one more thing do the turn signals opererate normal by themselves and if so turn on headlights do all the running/tail lights work normal then try turn signals with lights on does everything work,,,if OK to this point more then likely suspect something going on at turn signal switch /....keep in mind your brake light circuits go through the turn signal switch..

 

[newsome311]

good point about the brake light going through the turn signal switch. I had forgotten about that.

 

[gkling01]

If I'm not mistaken,, the ground for the lights are actually the screws that hold the light frame to the body. I've had these screws become loose and had ground issues because of this.

Sent from my SM-G965U using Tapatalk

 

[DirtDonk]

Correct. The tail lamp and brake/turn lamp filaments are grounded through the reflector assembly to the body via the screws. Only the reverse lamp has it's own independent ground with a wire to the body. This is because the reverse lamps were an afterthought and were added some time later in the '66 model year. You can even see that the backup lamp reflector is a separate piece that's riveted to the main reflector and insulated from it by a paper(?) gasket.
Hence the separate ground wire.

The main lamp housings/reflectors are also insulated by plastic squares so that the two metals don't actually touch. Only the screws create the interface for grounding.
If yours are very rusty and loose, this could cause trouble. If the housings have been painted, or the body was painted inside the screw holes, this could cause a problem.
Also if your main body ground was removed and never replaced during a battery cable change, this could be part of the problem at the very least. Not to mention that the bodies themselves get rusty where the panels were spot welded together at the factory. When they were new, no problem passing electrons from one panel to the other. After 50 years of rust and paint, it's not always so cut & dry.
So always check, fix, add and upgrade your vehicle grounds.

Paul