Troubleshooting Trailer with LED Taillights Where all Lights Shut Off When Running Lights are On

Question:

I installed new submersible lights on my trailer. It’s basic 4 way brown /yellow, green/brown one set down each side. I tapped a good solid ground bolt at the hitch end. The turn signals and brake function are fine. As soon as I engage the headlights for running, it cancels out the lights, turn signal on. Turn off the head lights it resumes. I’m using an adapter for the 4 way, since my truck has the 7 blade. I have a new 16’ with LEDs non submersible and it works great off the adapter. I even tested with the old lights and it does the same thing. I’m out of ideas. The perplexing thing is one trailer works off the adapter all functions.

asked by: Glenn C

Expert Reply:

I'd be willing to bet you have a short on the running light circuit of your trailer wiring that's touching the trailer frame which is causing your problems. Since the lights are grounding through the frame a short to the ground of all of the circuits will take out all of the lights that are using the frame as a ground.

Go over the running light circuit looking for any cut or exposed wire and fix as needed.

expert reply by: Jameson C