Troubleshooting Trailer Tail Lights Not Working For Brake Lights Or Left Turn Signal

Question:

I have a 4 wire small boat trailer wiring harness. Connected ALL wires carefully with proper electrical connectors and grounded the white wire to the boat trailer. My truck is 2016 Chevy Silverado 1500 with factory installed Flat plug or Round plug trailer connector. My problem...I cannot get the left turn signal or brake lights to come on. I only have right turn signal and trailer lights. Brand new submersible trailer lights, and new wires just ran loosely from lights to the trucks flat plug receptacle. A Could a bad trailer ground wire cause this? B There are no known issues with my trucks factory installed receptacle. Im so frustrated. I have no idea what else to try to resolve the problem! Brad

asked by: Bradley R

Expert Reply:

That is definitely a strange problem you are having Brad. Especially with the right turn signal working but the brake light is not since they both are powered off the same wire. I would start by checking your ground connections both at the lights and the ground from the trailer to the vehicle. You can try using a loose piece of jumper wire from the trailer lights to the vehicle to see if that helps to resolve the issues you are having. If that fixes it you know there is an issue with the grounds on your trailer.

If the ground is not an issue you will want to use a Test Light # PTW2993 to test along the harness to see where the power is either shorting out or if the wiring on your trailer is somehow damaged internally where you cannot see it.

expert reply by: Bud M