Troubleshooting Running Lights Of Trailer Not Working But No Truck Fuses Blown

Question:

Fuses are not blown. Wires seem to be in perfectly good working order, but I can’t get any fire or any power through to my running lights on my trailer. I don’t know exactly what’s going on.

asked by: Karl

Expert Reply:

I'm not sure exactly what all you've tested, but first things first you need to use a circuit tester like # PTW80157 to test the running light circuit of your trucks trailer connector, while the headlights are turned on.

If you have power in the connector then the issue is in the trailer, and if you don't have power the issue is in the vehicle wiring.

Assuming you've already checked that your trucks connector is putting out power then you'll want to check your trailer connector for corrosion that is green/white, as that can stop power from making it's way to the trailer. From there use the circuit tester to check the running light wire coming out of the connector, and keep testing the wire every few feet until power is lost.

Let me know what you find and I can go into a little more detail based on your specific truck/trailer.

expert reply by: Samuel C