Right Side Trailer Lights Not Working After Installing a Wiring Harness on 2011 Mitsubishi Endeavor  

Question:

Expert Reply:

A poor ground connection could cause one side of your trailer lights not to work. I would start by checking the ground connections on the trailer since the wiring harness that you purchased does not have a separate ground wire. The ground connections on your trailer should be clean and corrosion free. Check the ground connection for the trailer connector as well as the grounds for the trailer lights. You could also inspect the trailer side connector for any corrosion and clean or replace as necessary.

If that does not resolve the issue, you can test the wiring harness. Using a circuit tester like part # PTW2979, test the pins on the trailer connector. I have attached a video of my coworker demonstrating how to test a 4-flat trailer connector for you to check out. Make sure there is power on each pin while someone activates the light functions for the vehicle.

If the wiring harness on your vehicle is functioning properly, then we know the issue is somewhere on your trailer. Inspect the wiring looking for any pinched, frayed or damaged sections that could cause a short. You could also probe the wire at different areas working your way from the trailer connector to the lights. This will tell you where the signal terminates.

I have attached a help article on trailer wiring for you to check out when troubleshooting the wiring on your trailer.

If the wiring harness on your vehicle does not have any power for the right side lights, check the wiring harness connections. If the connections look good, test the wires going into the converter box. If you have signals for the right side brake lights and turn signals going into the converter box, but not coming out, that could indicate an issue with the converter box.

expert reply by: John H

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Bill D.

4/17/2013

I did not have the trailer on the hitch when I was working on the lights. Lesson learned.Thanks,Bill

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Patrick B.

4/24/2013

That means that it is getting a complete ground through the hardware. There is still a weak ground on the wiring which should be corrected. As the coupler moves on the ball and the ballmount wiggles in the hitch, you can lose that hardware ground and lights will flicker. But since the lights went back to proper function with the trailer all hooked up, a ground issue is the clear culprit.

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