Brakes Lights on Trailer Don't Work But All Other Light Functions Work

Question:

I replaced the lights and wiring on my trailer. I also replaced the harness to my vehicle. I have running lights and blinkers. But no brake lights The lights on the vehicle all work fine

asked by: Dan

Expert Reply:

The issue you are seeing with the lights on your trailer can be traced back to 2 different things; you have a weak or poor ground connection for your brake lights, or they are drawing too much power on that circuit.

Check the grounds on your brake light circuit (including on your vehicle side) and make sure they are solid and connected to a clean, bare-metal surface. Even some paint can cause some issues.

If that all looks good then try disconnecting the lights one by one and testing the brake light circuit in-between. Should they work after you have disconnected a light or lights then you know that you have too many lights on that circuit.

Let me know if this doesn't fix your problem and I can help you troubleshoot further.

expert reply by: Jon G