Troubleshooting Trailer Lights Not Functioning

Question:

cannot get my brake lights and running lights to work on trailer.

asked by: David

Expert Reply:

The first thing you need to do is determine if the problem is on the tow vehicle of the equation or the trailer. In order to do this you will need to use a circuit tester like our part # PTW2993 and test the circuits of the 4-way on your vehicle. Check out the video I attached on how to do this.

If there is voltage there then you know the problem is in the trailer wiring. I would start at the light assemblies and make sure the grounds are connected to a clean metal surface, or if the assemblies ground through the mounting hardware I would make sure the assemblies are attached to a clean metal surface as well. The next place to check would be the trailer connector. Check for corrosion or exposed wire that could cause a short. Besides that you would need to check the condition of the wiring from the connector to the assemblies.

If when you tested the connector the voltage was not on the vehicle side connector then the problem is on the vehicle wiring. The best way to address this would be to start at the connector and work your way back to where the 4-way connector installs checking for anything obvious that would cause the 4-way to not function like corrosion or cut wire and fix as necessary.

I attached an FAQ on trailer wiring for you to check out also.

expert reply by: Jameson C