Troubleshooting Reasons Why Boat Trailer Running Lights Are Not Working

Expert Reply:

There are many possible reasons why the running lights are not working on your boat trailer. First, I recommend checking the ground connections. Trailer lights usually ground through the mounting studs. They will need to be attached to a clean and corrosion free bare metal surface. If you recently added a plastic license plate cover, that could also be causing the problem.

You will also want to make sure that the main ground from the trailer connector is attached to a clean and corrosion free bare metal surface. Without good grounds, the circuit cannot be completed and the light will not work.

Check for corrosion on the trailer and vehicle side connectors. Corrosion on a connector will make for a bad connection and the lights may not work.

You can also check the wiring for the brown wire (carriers the running light signal). It is the wire next to the ground wire on the back of the connector. Check for any breaks in the wiring and make repairs as needed. The Optronics Wiring, # A20WB, is a wishbone type of harness. This means that it has one brown wire that goes to the left side, and another brown wire that goes to the right side. No jumper wire is needed from one light to the other.

If you still are having trouble, make sure that the running light circuit pin from the truck connector corresponds with the one on the trailer side. You can use a circuit tester like # 3808 to test the pins.

expert reply by: Michael H