Trailer Right Rear Tail Light Only Works Sometimes

Question:

My trailer has a 4 wire flat connector. My truck 2004 Silverado has a 7 pin connector. The two are joined using HM47570 Theres a couple of problems which occur under certain conditions listed below. With truck lights on, the trailer: Indicator L and R - both OK. Tail lights - both OK. Brake - right light goes off completely. Hazards - left illuminates with truck, right illuminates opposite to truck and left tail light. Right indicator works with brake light on. With truck lights off, the trailer: Indicator L and R - both OK. Brake - left seems brighter than right. Hazards - OK Any idea how I can solve this problem?

asked by: Bob

Expert Reply:

I believe that you are experiencing a ground problem, which can cause all sorts of weirdness. There are a couple of usual suspects that you can investigate to get to the source of the problem. First, make sure that the main trailer connector ground is attached to a clean and corrosion free bare metal surface.

Next you will do the same for each of the trailer lights. The lights with tail light kit # TL5RK ground through the mounting studs. Make sure those are also attached to clean metal surfaces.

Sometimes, a plastic license plate holder can interfere with a good ground if placed between the light and trailer frame. Also, if the trailer has an aluminum frame, tilt bed, or folding tongue you will want to run jumper grounds from the lights to the main trailer connector ground.

I have also included a link to our trailer wiring FAQ article for you.

expert reply by: Michael H