Both brake lights not working?

2002 CHEVROLET EXPRESS
167,500 MILES • 4.3L • 6 CYL • 2WD • AUTOMATIC
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TRINITY58
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Good morning!

Having an issue with both brake lights not working on my newly acquired cargo van. Have checked both bulbs and they are good. The bulb sockets are clean. Running lights and turn signals are working, as well as the third brake light above the rear doors. If I put the brake light bulbs in "backwards", the brake filaments light up on both sides. No trailer lights are installed. Suspect brake light switch, but don't know which wires to check with voltmeter.
Jan 20, 2023 at 7:48 AM
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STRAILER
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The brake lights are controller by the white wire and if the nigh mount brake light is working this mean this part of the circuit is working, use a test light to see if you have power at the white wire when the brakes are depressed, here is a guide to help:

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

Here are the brake light wiring diagrams or you can see how the system works.

This guide can help as well:

https://www.2carpros.com/articles/brake-lights-not-working

Check out the images (below). Please let us know what happens.
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Jan 20, 2023 at 5:58 PM
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TRINITY58
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Thank you for the diagrams Ken! Turns out there was a couple of issues...one was the contact bars inside both light bulb sockets were slightly bent downwards preventing a good connection with the bulbs. I straightened them up with a pick and had intermittent brake lights. Started to poke around with a dvm at the switch, and when I disconnected the electrical plug the whole brake light switch just fell apart. Looked like it was the original switch. The contacts inside the switch were burnt and one pair of contact points was just about wore out. Replaced the switch and everything works. Sorry for the delay in posting back, and thank you again for your advice. Hope this helps somebody else having a similar problem!
Apr 16, 2024 at 9:38 PM
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TRINITY58
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Forgot to add the picture...
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Apr 16, 2024 at 9:42 PM
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STRAILER
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Yep, that will do it, good find, and thanks for getting back to us. We are here to help, please use 2CarPros anytime.
Apr 17, 2024 at 9:37 AM