Trailer Right Turn Signal Does Not Work and Left Signal Comes On Instead of Right  

Question:

Helpful Expert Reply:

The first thing you are going to want to do is isolate the issue. Disconnect the trailer from the vehicle and use a circuit tester, # PTW2993 if needed, to test the wiring on the vehicle. If you are using an aftermarket converter on the vehicle first test the wires leading into the converter box. If the signals are not correct, then there is an issue with the vehicle wiring you will need to track down.

If the signals are correct going in but not coming out at the connector then that indicates a problem inside the converter and trailer wiring on the vehicle will need to be replaced. If the signals are correct going in and coming out then the issue is on the trailer wiring.

If the trailer lights worked properly before and this is a new development the issue is probably being caused by a bad ground connection and/or corrosion somewhere. First disconnect the trailer from the vehicle. Clean off any dirt or corrosion in the trailer connectors on the vehicle and trailer side.

Next make sure that the main trailer connector ground and the grounds for all of the lights are attached to clean and corrosion free bare metal surfaces.

If he trailer has an aluminum frame, tilt bed, or folding tongue then running jumper grounds from the lights to the main trailer connector ground can help. If you recently added a plastic license plate holder that fits between the trailer frame and the light, that can interrupt the ground. Attaching the plate holder elsewhere will help.

You will also want to check the trailer wiring for any broken or loose wires that may be causing a short. Exposed copper strands touching the metal of the trailer should be fixed and taped up. I have linked some FAQ articles and videos that will help you.

expert reply by: Michael H

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