Troubleshooting A Turn Signal That Is Not Working On My Trailer

Expert Reply:

This is something that can be remedied, but it will take some troubleshooting. This will be easier if your wiring harness is something like the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector, part # 118578. This is a plug and play system, so you will not have to check any spliced wires during the troubleshooting. If your setup is something like the 4-Pole Trailer End Connector, part # 18004, you attached to your question, you may have to do some wire splicing.

I recommend having a couple of items on hand when you start to troubleshoot your wiring. You can test specific 4-way wiring with the Curt LED 4-Way Flat Connector (Vehicle End) Tester, part # I26, and test to see if wires are hot with the Hook Probe Circuit Tester, part # PTW2993.

You are going to be testing for the following issues:

Your harness wires are not connected securely,
If you have a plug and play harness, the connectors are not seated properly,
You have a blown fuse or relay,
If you have a hard wired system, your brakes and turn signals have separate wires, and
Your ground is insufficient or you have a short to your ground.

I have included product description links, some helpful video links, and a weblink to trouble shooting your trailer wiring below.

expert reply by: Mark S

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