Testing a Trailer and Vehicle for Wiring Problems When Trailer Lights and Brakes Do Not Work

Question:

just got a used trailer and the light dont work it is a 7 pin plug and it has trailer brakes and i dont think they are working either no light at all no brake light or running light

asked by: Shawn

Expert Reply:

First, you will want to make sure that your towing vehicle and the trailer have connectors that are compatible. I have included a link to our wiring FAQ that covers what the functions should be on various connectors. Use a circuit tester like # PTW2993 if needed to test the pins on the towing vehicle. Then you will need to determine if the trailer side connector is wired the same way by tracing the wires back from the connector.

You will also want to make sure that the vehicle side and trailer side connectors are properly grounded to clean metal surfaces. On the trailer side all of the lights will also need to be grounded to clean metal surfaces. If there is any dirt or corrosion at the grounding points or inside the trailer connectors, or even in the back of the connectors where the wires attach, clean it out.

In order to operate the trailer brakes, you will need to have a brake controller in the towing vehicle. If you can tell me the year, make, and model of the vehicle i will be happy to make some suggestions.

expert reply by: Michael H