Loss of Power to One Side of Trailer Connection  

Question:

Expert Reply:

In order to determine what the problem is you will want to do some testing. First, disconnect the trailer from the vehicle. Then use a circuit tester, #PTW2993 if you need one, to test the vehicle side trailer connector. Have someone sit in the vehicle and run through the various functions while you test the connector.

If there is no power on the one side at the vehicle, then that indicates an issue on the vehicle side. There could be several reasons for this but to narrow them down I would need to know the year, make, and model of the vehicle, and whether or not it has factory wiring or aftermarket. If it is factory there could be a fuse or relay that has gone bad. Use the vehicle owner's manual to find fuse/relay locations.

If everything works on the vehicle side, then the issue must be on the trailer. With the trailer disconnected make sure the trailer and vehicle side connectors are clean and free of corrosion inside and out. Make sure the main trailer connector ground and grounds for all of the lights are attached to clean and corrosion free bare metal surfaces.

You will also want to check the wiring on the trailer for any breaks and loose connections. If the trailer has an aluminum frame, tilt bed, or folding tongue, adding jumper grounds from the lights to the main trailer connector ground will help. Also, if you recently added a plastic license plate between a taillight ground and the trailer frame then that can cause a ground interruption. I have included some links that should help.

expert reply by: Michael H

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