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Running Lights Not Working on Trailer After Installation of Optronics Trailer Light Kit # TL5RK


my signal light work as well as brake lights but running lights do not illuminate. What is my problem?


Expert Reply:

There are many possible reasons why the running lights are not working on your trailer when using the Optronics Trailer Light Kit, part # TL5RK.

First, I recommend checking the ground connections. The trailer lights on this kit will ground through the mounting studs. They will need to be attached to a clean and corrosion free bare metal surface.

You will also want to make sure that the main ground from the trailer connector is attached to a clean and corrosion free bare metal surface. Without good grounds, the circuit cannot be completed and the light will not work.

Check for corrosion on the trailer and vehicle side connectors. Corrosion on a connector will make for a bad connection and the lights may not work.

You can also check the wiring for the brown wire which will carry the running light signal. It is the wire next to the ground wire on the back of the connector. Check for any breaks in the wiring and make repairs as needed. The wiring harness in the # TL5RK kit, is a wishbone type of harness. This means that it has one brown wire that goes to the left side, and another brown wire that goes to the right side. No jumper wire is needed from one light to the other.

If you still are having trouble, make sure that the running light circuit pin from the truck connector corresponds with the one on the trailer side. You can use a circuit tester, part # 40376 to test the pins.

I am including a link to a FAQ page on trailer wiring that will help you troubleshoot your wiring harness. Also, I am including a link to a video that will describe the wishbone trailer wiring harness and how it is wired to the trailer.

expert reply by:
Jeff D

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