Troubleshooting Trailer Running Light Circuit

Question:

Put new Led lights, wire,and plug on trailer. Tested it with tester and everything works. Put on RV everything works but the tail lights. Tested RV socket, tester said everything I good. Put new socket on RV, still does not work.

asked by: Rudy

Expert Reply:

If you have tested the plug on the RV, and each circuit is functioning, then the problem lies either with the trailer connector on the trailer, or in the trailer wiring itself. A loose connection or insufficient ground connection is the most likely culprit.

First, check the connector on the trailer, look for any corrosion or damage that would prevent the signal from the running light circuit from getting through to the trailer. Then, make sure the white ground wire from the trailer connector is securely connected to a clean, non corroded spot on the trailer frame, usually on the trailer tongue. Trace the running light circuit, which is typically carried by a brown wire from the trailer connector all the way back to the lamps. Look for any pinched wires or loose connections. Make sure each lamp is grounded to the trailer frame, either through the mounting studs direct connection to the trailer frame or by a ground wire on each lamp.

I will link you to our trailer wiring troubleshooting FAQ article that you might find helpful.

expert reply by: Mike L