With Running Lights or Brake Lights On Turn Signals on Trailer Alternate

Updated 08/20/2014 | Published 08/19/2014

Question:

My truck has a 4-wire flat and a good clean ground. My boat trailer as a westbar wishbone 4-wire flat. The trailer has a good clean ground at the front. The driver side light is wired yellow/red and brown/black. The opposite side is wired green/red and brown/black. The oddity is that both lights have a white ground. The lights are westbar 102640. The running lights work, left and right turn signals work and the brake lights work. Lights alternate when the headlights are on when either left or right turn signal on or when the brake is applied they also alternate. The turn signal side appears to be a bit brighter. Are the grounds on the lights causing the issue?

asked by: Roger

Helpful Expert Reply:

Tail light ground wires are usually white so that doesn't seem odd. This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

expert reply by: Michael H