Trailer Left Turn and Brake Light Not Working, All Other Lights Work  

Question:

Expert Reply:

First it is a good idea to verify that the vehicle side connector is fully functional without the trailer connected. Have someone sit in the vehicle and go through the lighting functions while you test the vehicle's connector using a circuit tester such as # PTW2993. If the left turn signal/brake light pin does not show power when it should then there is a problem on the vehicle side. There may be other fuses or relays associated with the tow package wiring. Use the owner's manual to find the fuse and relays locations just in case you missed one.

If everything is working on the vehicle side, then the issue is on the trailer. It could be a bad ground, broken wiring somewhere, or a problem with the left light itself. Make sure the vehicle and trailer side connectors are clean and free of corrosion. The main trailer connector ground and the ground for the light needs to be attached to a clean and corrosion free bare metal surface. If there is anything between the trailer frame and the light ground, then that could interrupt the ground connection. Or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

Inspect the wiring from the trailer connector back to the light and fix any broken or pinched wires as needed. If the light still isn't working, then it could be something internal to the light or even a bulb that needs to be replaced.

expert reply by: Michael H

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