Attaching Some Lights On Trailer Causing Other Lights To Stop Working

Updated 07/23/2014 | Published 07/21/2014

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Optronics Incandescent Trailer Fender Light - Submersible - 2 Bulbs - Red/Amber Lens

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$4.44

Hook Probe Circuit Tester

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Question:

Hello I had a trailer fire so Im rewiring the lights, the two rear lights work when I Hook the fender lights to the brown wire the lights shut off. Is there a bad ground or what?

asked by: William S

Expert Reply:

It sounds like there's a possibility you are overloading the circuit, and that could be causing the issue. Or there may be a short in the lights on the fender of your trailer, or in the taillight circuit which is attached to the brown wire on the wiring harness. You will want to make sure you are using the correct wire gauge when wiring the trailer. If possible, I recommend using the heavier gauge wire so that you are sure it can handle the load.

The first thing I recommend is to test the vehicle harness using a circuit tester like part # PTW2993. If all of the functions work, then you can move on to the trailer.

You will want to inspect all of the wires for any signs of damage. Since you said you had a fire, the wires may not have obvious signs but may have been damaged. You will want to look for breaks in the wire or places on the wiring that the outer jacket is missing or damaged. Make sure all of the grounds for the lights are secured. A loose ground or one with a short can cause many problems.

I have attached a helpful troubleshooting article that explains what to look for when the lights are not functioning as intended.

I am also attaching a helpful article that explains trailer wiring and how the wires need to be run you can check out.

expert reply by: Jeffrey L