Troubleshooting Brake Light Wiring Issue on Trailer  

Question:

Expert Reply:

With running and parking lights, you most likely don't have a ground issue from the housing but it doesn't hurt to test that and see if it fixes your issue. Sometimes a common ground is the best solution. Another possibility is that your vehicle side connection may not be functioning correctly due to a fuse or a bad ground there.

I recommend you start by putting a circuit tester like # PTW2993 on your vehicle side connection when the trailer is not connected to test functions. If those functions don't check out, you've isolated the issue to the vehicle. If they do check out, then you've isolated the issue to the trailer. You can connect a 12V battery to your trailer by running a wire from the negative terminal to the ground on your trailer frame and then from the positive battery terminal run a wire to connect to each individual wire function pole. You've already isolated the ground, so you can test the running lights which will light both sides, the right turn and stop wire which will light the right side only, and the left turn and stop wire which will light the left side only. If these functions don't work, you either have a ground issue or you have a short in the wire. You can use the circuit tester to locate any short and replace the wire as needed.

If you don't want to hassle with replacing sections of wire, you can simply rewire the trailer using the Optronics 35 ft. Wishbone 4-Way Trailer Wiring Harness with 42" Ground Wire # A35W42B. I've attached a video to assist.

expert reply by: Jason S

0