Troubleshooting Trailer Taillight Assemblies that Do Not Function

Question:

I have rewired a small boat trailer with #TL5RK. The side marker lights work, but the running lights and turn signals do not. I understand the grounds for this kit is the light studs. I recently repainted the trailer. I scaped to bare metal where the studs pass through the trailer frame and tighted the nuts, but they still will not work. There is power to the trailer and a good ground at the harness because the marker lights work. The lights work when I test them on my 12V lawnmower battery. I have rechecked all the connections and confirmed the wiring is correct. I am into my second day on this and becoming quite frustrated. My vehicle is a 2013 Ford Explorer with a tow package. I am using a 7-pt plug that the four point harness goes into. The Optronics instructions says if your towing vehicle has turn signals separate from the stop lights, an electric turn signal converter will be required. The vehicle does have separate amber turn signals, but I would think this should not effect the running lamps. The previous trailer lights worked fine until they wore out from numberous water submersions. Whats the solution to my dilema? Thank you

asked by: Larry M

Expert Reply:

The problem is either in the power to the light or the ground of the light. I would use a circuit tester like our part # PTW2993 to probe the wire leading into the assembly with the circuits on to see if the power is making it to the assemblies. If so, then you know the problem is in the ground. Since you already double checked to make sure the assembly is installed on a clean metal surface your next option would be to run a jumper wire from each assembly back to the main ground of the trailer.

If the power is not making it to the assemblies you would need to trace the wire from the connector on the trailer back to the assembly fixing any obvious shorts as necessary.

I attached a couple FAQ articles on trailer wiring for you to check out also.

expert reply by: Jameson C