Troubleshooting Trailer Brake Lights Not Functioning

Question:

Running lights but no brake lights.

asked by: Steve

Expert Reply:

The first thing I would check would be the left/brake and right/brake circuits of the trailer connector that is on your vehicle. You will want to use a multimeter like our part # PT89ZR to test for voltage when the brakes are applied. If there is voltage there with the brakes applied then you know the problem lies in the trailer wiring, and it most likely is that there is a ground problem on the trailer wiring.

You will want to check the wiring of your trailer for loose wiring, corrosion or anything else that could cause the circuit short. Most likely the problem is on the ground side of the wiring and the additional amperage that is required to illuminate the brake lights is too much for the circuit so the brake lights do not work.

If there is not voltage on your vehicle-side trailer connector then the problem lies somewhere in the trailer wiring of your vehicle. You might want to trace the wiring back looking for corrosion, exposed or loose wiring and anything else that might short out wiring and fix as necessary.

expert reply by: Jameson C