Troubleshooting Brake Lights that Turn off when Brakes Applied

Question:

I just rewired my trailer and everything works fine except when I apply the brakes the right side goes out. no lights

asked by: Chris

Expert Reply:

It sounds like you have a ground problem on the trailer. I'd start by checking the ground wire at the trailer coupler and making sure it is connected to a solid clean paint free spot on the coupler or frame. Then I would check the tail light assemblies.

Tail lights are usually grounded through their connection to the trailer frame. If you have a plastic license plate bracket on the left side this could be the culprit. You should also check the brackets that hold the lights. If they are bolted to the trailer frame you should remove them and clean any rust and corrosion from between the bracket and trailer frame.

These steps should get you rolling, if not check for a broken pinched or frayed wire somewhere along the trailer frame. We have some videos that demonstrate how to troubleshoot linked at right.

expert reply by: Chris O