Brake light issues

[chrismoore701]

Ok i am not sure what is going on yet. Brake lights went out on Thursday. Got home seemed like the switch was bad. Piece of cake. Swapped out all was good. Drove her today and was good at first and went out again. Came home parked her around noon. Just went back out and they work again. Checked the plug checked the switch. All works. Could this be something that quits after driving for a bit? Seems strange. I have the dash pulled apart to have easy access to the switch. I’m going to drive it for a while and see if it happens again. Everything else works. Signals. Flashers. And lights

1979 c10
4000 miles on a frame off
New painless harness

Thoughts?

[70GMCer]

I just went thought this myself.

Check the wiring plug under the rear cross member. It might have come loose.

Pull it apart & check for corrosion.

I use di-electric grease on all my connections.

Also check for the ground wire behind the lens to make sure it is grounded properly.

[chrismoore701]

On it. But if that were the case the flashers and turn signals would also not work correct.

[chrismoore701]

Any other thoughts?

[Dead Parrot]

If you can have someone follow you, pull the connector off the switch and jump across the connector so the brake lights are always on. Now go for a drive, preferably on some rough roads. If the brake lights blink, loose connection somewhere.

Might be worth it to replace the switch on the thought that if it is the original, it may be getting a bit worn after about 39 years.

[chrismoore701]

I like your thoughts on jumping the wire, will try that
The first time they went out was with the original switch. Pulled it out and tested it and it was bad. Bought a new one and all was good.
Then the problem came back with the new switch. Pulled the old one out of the garbage and pulled it apart. It worked. Could be a freak thing, could also be the switch again.

But as mentioned, everything else works when the brake lights stop working. Flashers, turn signals, and tail lights. This is what makes me think it is the switch.

[silvereagle07]

I had a similar issue on my 85 4x4. Go to the stop light switch on the white wire, If I remember correctly, and test for power there. Then test it coming out of the stop lamp switch. I assembled a 3157 bulb with leads soldered on them to eliminate an open in the wiring. If there is an open or frayed wire a volt meter will show the correct voltage but it will not carry the load that the bulbs require.