Trailer Right Side Running Not Work, All Other Trailer Lights Work

Updated 08/31/2015 | Published 08/29/2015

Question:

I have all my triler lights working except the R tail light/running light part..brake and blinker are fine. checked at truck 6 pin plug and NO test light at tail/running light. Fuse for brake and running same.

asked by: Dennis

Expert Reply:

If you are not getting power on the running light circuit at the connector on the truck then none of the running lights should be working on the trailer. Trailer's in the US use one circuit for running lights, one circuit for left turn/brake lights, and one for right turn/brake lights.

So if just the right side running light is not working then it is likely a bad ground or wiring issue somewhere on the trailer. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

You can also inspect the trailer wiring to that light and fix any damaged or pinched wires. I have also included a couple of links on trailer wiring that should help.

expert reply by: Michael H