Troubleshooting Trailer Lights that Turn and Brake Doesn't Work When Truck Running Lights are On

Question:

I recently purchased a set of the Streamline LED taillights. When I have the headlights off in my towing vehicle the lights function as they should. But when the towing vehicle has its lights on or day time running lights, the trailer running lights come on as they should but the taillights come on and stay lighted up, but the brake lights and neither turn signal will work. I checked the ground on both lights and it seems to be good and the ground from the wiring harness is also tied into the ground of one of the lights.

asked by: Jay

Expert Reply:

What you're describing is typically a ground issue. But you've checked the grounds so it must be a short. You might try cleaning each ground connection just to be sure if you haven't already.

Next I would clean both connectors on the tow vehicle and trailer. Also use a circuit tester on the vehicle's connector to make sure the issue is definitely on the trailer. If the problem is on the trailer trace the wiring back to the lights looking for any damaged or pinched wires. If the problem is on the vehicle then check the ground on its connector. Then inspect its wiring like you would have on the trailer.

If you still can't find the issue let me know what you did find and we'll keep troubleshooting.

expert reply by: Charles S