Brake Lights Turn Off when I Step On the Brakes After Wiring New Trailer Lights

Updated 03/10/2010 | Published 03/08/2010

Question:

Installed 2 new tailight assemblies left and right on the back of my trailer -yellow on the left and green on the right -I wired them up -checked them out -both running lights and turn signals worked fine. However, when I stepped on the brakes to check the stop lights -everything went out! I then let off the brakes -everything came back on -Question? is this a grounding problem? Everything seems hot and wired properly!

asked by: Jan F

Expert Reply:

Yes, it seems like you have a ground problem on the trailer. I would 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 of 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 then 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.

expert reply by: Robert G