Brake lights not working?

BRIAN POWERS

MEMBER
2000 GMC C3500
V8
2WD
AUTOMATIC

Hi, no brake lights on my 3500 Gmc, swapped relay under hood with another truck, didn't work. Can't reach stop light switch to test power so swapped out switch with working truck, didn't make a difference no lights. Checked wiring from connector at fire wall to lights, all good was able to power up lights. Where do I go from here to find out if my interlock solenoid is bad if the brake light system is not working. Am I missing a relay or switch somewhere? I also checked fuses, and all other light systems are working fine (hazards, blinkers, park and drive lights. Thanks Brian

5 Replies

WRENCHTECH

MECHANIC
20,757 POSTS

Is the 3rd (high mount) brake light working? It sounds like the turn signal switch could be bad but to be sure this guide will help test for power with the brake light wiring diagrams so you can see how the system works.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the diagrams (Below). Please run this test and get back to us.

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Wednesday, March 2nd, 2011 AT 11:04 PM

RASMATAZ

MECHANIC
75,992 POSTS

Check and test the stop lamp relay and the turn and hazard switch-the brake circuit goes thru there

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Wednesday, March 2nd, 2011 AT 11:07 PM

BRIAN POWERS

MEMBER
3 POSTS

I've checked the 3rd brake light, it does not work either. I have swapped out the relay under the hood with a working one from another truck and it made no differance. I have working turn signals and hazard lights, also have parking lights. Is there another relay somewhere other than under the hood? Also would the power for the brake light go to the turn signal switch first and then to the stop switch? Thanks Brian

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Wednesday, March 9th, 2011 AT 6:11 PM

WRENCHTECH

MECHANIC
20,757 POSTS

You're going to have to test for power coming in and out of the brake light switch.

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Wednesday, March 9th, 2011 AT 7:05 PM

GRIMMS

MEMBER
1 POST

Just fixed it! The orange wire under the fuse box under hood was corroded and broken. I was told to look for a orange and or a white wire. Fixed wire and lights and my cruise returned. Hope this can help.