Electrical Problem
 

Tail lights and brake lights work fine with head lights off.

When I turn the headlights on.....the brake lights come on.

Cant see where I have any wires crossed.

Any body had this problem?

Re: Electrical Problem
 

so does everything work fine when you pull the switch out once for park lights?
did this issue just pop up? is this original wiring? do you have a trailer harness?
do you have good tail light housing grounds?

need more info.

Re: Electrical Problem
 

Sounds like a ground is not hooked up in the back.

Re: Electrical Problem
 

I think you are both right. I think the ground is gone and I am back feeding.

Rippin it apart now.

I remember the light socket was a 2 wire and the PO had wrapped a wire around the metallic base for a ground. That may be the whole problem!



10gmc63...

66 truck
79 harness and fuse box hootus
no trailer harness

Re: Electrical Problem
 

Attachment 446939

Fixed it!

Kinda......

The old lights had a 2 wire socket and a 3rd wire wrapped around the metallic base and covered in tape for a ground.

The 3rd wire wasnt a good enuff ground, so the tail lights were back feeding thru the brake lights.

I removed the bulbs from the bed tail lights and everthing started correctly.

I guess I need to find some late model 3 wire light sockets.

Re: Electrical Problem
 

I had tail issues for a long time. I finally pulled the housings apart completely including the pigtail that drops down inside the tailgate. I found the springs that compress when you install a bulb were getting hung up and not making contact with the bulb. I sanded the inside of the socket to clean them and I lubed up the contacts best I could. I re-did the mounting screws and clips also. It took all of the stuff being reworked and cleaned to get it working properly, and its confusing as hell when they are doing all that weird stuff.