Troubleshooting Trailer Turn Signals that Operate Backwards

Published 10/02/2015

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

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$80.89

Hook Probe Circuit Tester

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$13.21

Question:

I do have a problem. When I hooked up my camper trailer this summer. This was the first time I used the wiring harness. I find out when I use my right turn directional the left trailer light goes on. And vice versa? I looked if I crossed the wires, but it has to go that way because one wire is longer to reach to the driver side in the back. Do I have to add more wire to switch this?

asked by: Jack

Expert Reply:

It sounds like you may have installed the connectors of your trailer wiring on the wrong sides of the vehicle, or your trailer is wired backwards.

First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.

The yellow wire of the 4-way should be carrying the left turn/stop signal and the green wire should be carrying the right turn/stop signal. If this is correct then you should check your trailer's wiring for backwards wiring and fix as necessary.

If the problem is on the vehicle a very easy fix would be to cut the yellow and green wires leaving enough room to reconnect them and then swap the two wires. So you would run the yellow to the green and the green to the yellow. That would reverse the circuits without forcing you to completely reinstall the trailer wiring.

expert reply by: Jameson C