Trailer Lights on Rental Trailer Cut Out Once Vehicle Headlights are Switched On

Question:

I have a CURT 56146 lighting unit installed on my 2006 BMW X3. I rented a UHaul trailer with LED lights and it worked fine until the vehicle lights were turned on for night driving. Whats up?

asked by: Randall B

Expert Reply:

What you mention is a classic system of a ground problem. Everything works fine until the running light circuit is activated, at which point the trailer's taillights are drawing maximum amperage. If there's a ground problem, this is where it's going to show up.

On the vehicle side, make sure the white ground wire is securely attached to clean metal on the vehicle frame or chassis, but the chances are that the ground problem is somewhere in the wiring on the trailer itself. The main ground from the trailer connector grounds to the trailer frame, usually on the trailer tongue. Make sure this connection is tight and not corroded.

Since it's a rental trailer and not something you own, I'm not sure how much you're willing to dig into it but those are the most likely places to locate the problem.

expert reply by: Mike L