Trailer Light Troubleshooting With a T-One Vehicle Wiring Harness With 4 Pole Connector

Question:

I installed the harness for my 2001 Chryler Voyager. The trailer lights will not work correctly. When the running lights are on the right is bright like a brake light and the left is weak The left side blinks with either the left or right blinker activated on my van. Only the brake light on the left works. I have checked all the grounds on the trailer and on the van. I connected another trailer to my van and it had the same problems. I connected the trailer to another vehicle and it worked fine. The lights on the van work fine with or without the trailer. I have used three different harnesses with all the exact same results. Please help!

asked by: Matthew R

Expert Reply:

Since the issue is persistent with multiple trailers that pretty much leaves the vehicle wiring as the issue and since the problem is persistent with multiple wiring harnesses it leads me to believe the issue is one of two things. The first and easiest issue to check would be to make sure there are no bent pins on any of the connectors on the wiring harnesses or on the vehicle connectors.

If all of the pins look straight, then there is probably a grounding issue. I would relocate my ground wire and one trick we have used to eliminate any possibility of a faulty ground is to run a temporary ground wire directly from the negative terminal of the vehicle battery to the ground wire on the trailer wiring harness.

expert reply by: John H