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Troubleshooting Wiring When Trailer Left Turn And Brake Lights Are Not Working


I have lights working on both sides. But on the left side no brake lights or turn signals work on utility trailer


Expert Reply:

The first thing you will need to do is disconnect the trailer and then use a circuit tester like part # PTW2993 to test the trailer connector on your vehicle.

Have someone sit in the driver's seat and run through the functions while you are testing the connector. If all of the functions are working properly then that indicates a problem on the trailer side.

If you find there is a problem on the vehicle side connector test the wires that lead into the back of the connector. If you find they are not working, then there is a wiring issue on the vehicle side that needs to be fixed.

If everything checks out okay on the vehicle side the issue is going to be on the trailer. The first thing to do is check out the trailer connector for any signs of dirt or corrosion and clean it up. Make sure the grounds are in good shape and show no signs of corrosion and are securely fastened to a clean metal surface. Check the wiring on the trailer for any signs of broken or pinched wires.

If all the grounds are attached to clean metal surfaces it could be the trailer causing the problem. If you have an aluminum trailer, tilt trailer or tongue then you would need to run jumper grounds from the lights to the main trailer connector ground.

expert reply by:
Jeffrey L

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