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....THEY WORKED before I installed the switch. Installed it and.....no brake lights. Any help is welcome.
Also, dash lights aren't working.......��

[mr48chev]

Dig out your test light and see if you have power to the switch.

I'd check the fuse because it is easy to pop the fuse when you are moving those hot all the time wires around.


With that you might also want to check the hot wire from the fuse block to the brake light switch to make sure that it hasn't rubbed on metal and shorted out.

[RustyPile]

If the lights came on when you plugged in the switch, you don't have a fuse or wiring problem.. the switch has to be adjusted correctly when you install it.. It sounds like the switch needs to be adjust farther away from the pedal arm...

[pontiacvince]

Bought a new head light switch and the dash lights are working again. Still no brake lights with either the old or new switch just hanging from the plug. As I said when I bought the new brake light switch, it worked when just hanging from the plug. Now it won't. Continuity is good in both switches. Fuses are all good. I really don't want to get pulled over, or worse, have some jackass run into my Suburban because the brake lights aren't working. All other lights are good.

STUMPED!!!

[dmjlambert]

The next thing to test is the turn signal switch. These wire colors are on the wiring harness side of the connector going to the steering column wiring.

purple - power from turn signal flasher
brown - power from hazard flasher
white - brake light power
black - horn button
light blue - left front turn signal light
dark blue - right front turn signal light
yellow - left rear turn signal/brake light
green - right rear turn signal/brake light

Leave the steering column connected to this connector, and insert a test probe into the back of the wiring harness side connector at the points you want to test. The interesting colors in your case are white for brake light power. Make sure the white wire has 12V with brake pedal pressed, and doesn't have 12V with brake released. If that works repeat the test at the yellow and green wires.

Follow the wiring diagram in the service manual for your truck's year. Or here is a general purpose 67-72 diagram https://67-72chevytrucks.com/vboard/...27#post9186727

[pontiacvince]

Originally Posted by dmjlambert

The next thing to test is the turn signal switch. These wire colors are on the wiring harness side of the connector going to the steering column wiring.

purple - power from turn signal flasher
brown - power from hazard flasher
white - brake light power
black - horn button
light blue - left front turn signal light
dark blue - right front turn signal light
yellow - left rear turn signal/brake light
green - right rear turn signal/brake light

Leave the steering column connected to this connector, and insert a test probe into the back of the wiring harness side connector at the points you want to test. The interesting colors in your case are white for brake light power. Make sure the white wire has 12V with brake pedal pressed, and doesn't have 12V with brake released. If that works repeat the test at the yellow and green wires.

Follow the wiring diagram in the service manual for your truck's year. Or here is a general purpose 67-72 diagram https://67-72chevytrucks.com/vboard/...27#post9186727

I tried pulling the turn signal switch from the column, but there is a lip on the inside of the CPP tilt column that prevents the switch from coming out.....

[dmjlambert]

You don't have to pull the turn signal switch or even disconnect it to test it.

[twoskies]

just a suggestion
ive used the trailer wiring setup with the magnetic lights before, wired a connector into where it goes right by the firewall
just used to verify my wiring or switch

i had a grounding issue, fixed and ok

was a 1972 chevy c10, yours might be different