Electrical

[pontiacvince]

I've been chasing some electrical gremlins in my '71 Suburban for a while now. My brake lights stopped working. I tried adjusting the stop light switch. I've checked fuses. I've checked bulbs. I even bought a new brake light switch. Unplugged the wire from the old one, plugged the new one in and while just hanging from the plug THEY WORKED! I installed the switch and they quit working again. Continuity is good on both the new and old switches. Any help is welcome.

[RustyPile]

Originally Posted by pontiacvince

I've been chasing some electrical gremlins in my '71 Suburban for a while now. My brake lights stopped working. I tried adjusting the stop light switch. I've checked fuses. I've checked bulbs. I even bought a new brake light switch. Unplugged the wire from the old one, plugged the new one in and while just hanging from the plug THEY WORKED! I installed the switch and they quit working again. Continuity is good on both the new and old switches. Any help is welcome.

I highlighted a sentence in your post.. That statement absolutely proves the wiring, switch, bulbs, and fuse are all working as they should.. No need for any more testing.. If you adjusted the brake light switch, your procedure was flawed.. Consult the 1971 Factory Service Manual, section 12, page 3 for the proper procedure..

[pontiacvince]

Originally Posted by RustyPile

I highlighted a sentence in your post.. That statement absolutely proves the wiring, switch, bulbs, and fuse are all working as they should.. No need for any more testing.. If you adjusted the brake light switch, your procedure was flawed.. Consult the 1971 Factory Service Manual, section 12, page 3 for the proper procedure..

The switch should work now just hanging from the plug like it did when I first bought it, but it doesn't. Continuity still tests good.

[HO455]

I would do a voltage check at this point. Put the black lead on a known good ground. The red lead to the one of the switch terminals and check voltage. Then do the same for the other terminal. One terminal should have battery voltage on it the other zero volts.

Now do the checks with the brake switch operated or closed. You should see battery voltage on both sides of the switch now. If the voltage drops significantly then you have a bad connection between the switch and the fuse block buss work.