Troubleshooting Trailer Brake Lights Not Illuminating

Question:

All is wired correct but I have no stop lights on either of my two trailers. Put the trailers on another truck and all works correct

asked by: Leo

Expert Reply:

It sounds like you have eliminated the trailers as being the problem since they work fine with other trucks.

I would first recommend you double check how the trailer wiring harness is installed on your vehicle, make sure all of the connections are good and tight. You should check all towing related fuses and relays as well. You can also use a circuit tester like part # PTW2993 to verify that the brake lights are/aren't working from the trailer wiring harness on your vehicle. Check out the video I attached.

Since the brake lights tend to draw the most amperage, and since both of yours aren't working, I would be inclined to think there is a ground problem somewhere on your vehicle's trailer wiring. Or the trailer could still be at fault. Your truck may have a weaker trailer wiring circuits so the bad grounds aren't noticeable with a different truck. You can try improving the grounds of the trailer wiring by running the grounds of the light assemblies back to the main harness of the trailer wiring.

expert reply by: Jameson C