The brake lights do not work with the headlights on

2000 DODGE RAM

175,000 MILES • 8.0L • V10 • 4WD

T. LANDERS

MEMBER
1 POST

The truck listed above is a 2500 SLT V10. I switched the brake lights to LED bulbs. The brake lights will not work when I turn on the headlight switch. They both work fine without the headlights on. All fuses good. All the bulbs are new. I also changed back to regular original bulbs to see if that would fix the issue. It did not. Everything worked okay before the bulb upgrade. Any ideas?
Thanks

Feb 14, 2022 at 11:56 PM

WENDY W

✓Experienced Mechanic
86 POSTS

Hello!

It sounds like there may be a weak ground in the brake light circuit, which could cause the issue you are describing.

With the headlights on, you may want to use a test light to check for both power and ground at the brake light socket. Please check out the diagrams (below) of the exterior light circuits. The schematic is on two pages. The highlighted portion shows the ground side of the brake light circuit.

Here are a couple of repair guides and a video that can help you with those tests:

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

https://www.2carpros.com/articles/how-to-check-wiring

https://youtu.be/Hlna_kUt7As

Please let us know what you find, and we would be happy to offer further assistance.

Thanks, Wendy W

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Professional Diagram for 2CarPros Members
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Feb 15, 2022 at 10:18 PM

Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.