Troubleshooting Trailer Running Lights Not Functioning

Question:

Trailer running lights are not working. Hazards, blinkers, brake lights are. I dont believe the problem is on the truck side because I tested trailer on 2 different trucks same issue both trucks. What do I check Next? Trailer ground? Bad or cut running light wire?

asked by: Ryam C

Helpful Expert Reply:

Sounds like the running light circuit on the trailer is damaged to some extent. First thing I'd check for is corrosion on the running light pin of your 7-way which is the pin in the 1:00 position as you face the trailer connector. Corrosion here or the pin being bent will prevent the circuit from activating. If that's not the problem you'll want to trace the circuit back to the light assemblies and see if there's any cut or exposed wire and fix as needed. If the problem was ground related it most likely would have prevented other circuits from activating, but you can try improving the main ground of the trailer wiring harness to see if that helps.

I attached a couple help articles on trailer wiring for you to check out as well.

expert reply by: Jameson C