Troubleshooting Trailer Tail Lights that Do Not Function When Headlights are On

Question:

I have directional lights, and running lights, directional dont work when running lights on, 7 wire plug on camper

asked by: John

Expert Reply:

It sounds like you have a ground issue. When the headlights are on and the brakes applied, the highest amperage draw is placed on the wiring system and, a faulty ground will show at this time. Make sure you have good metal to metal contact. Paint and corrosion can act as insulators, so make sure the grounds of the light assemblies are touching clean metal. I would check all of the ground connections on the trailer.

First, check the ground at the trailer tongue from the trailer conenctor. Take the ground loose and clean the connection point on the trailer and the wire end. Next, check the trailers tail lights. Most tail lights are grounded through the mounting bolts to the trailer frame. Make sure the bolt connections are clean and solid. If your trailer lights are grounded by a separate ground wire make sure that wire is attached to a good, clean ground.

I attached an FAQ on trailer wiring for you to check out as well.

expert reply by: Jameson C