Troubleshooting Trailer Lamps on Ranger Boat Trailer Pulled by 2021 GMC Sierra That Aren't Working

Published 08/19/2021

Question:

I have a 2021 GMC Sierra and my 1993 ranger boat trailer lights won’t work with it. I can plug the1993 ranger trailer in my older truck and the lights do work. I can plug in my 2021 GMC Sierra to a 2010 bullet boat and the lights work. What do i need to do to get the 2021 GMC Sierra to work with the 1993 ranger. By the way Gmc hasn’t been any help on this matter. Thanks,clyde

asked by: Clyde A

Expert Reply:

The most likely cause of what you have going on is a poor ground connection on the boat trailer. Some vehicles are more picky about ground connections than others, which would explain why the boat trailer is working well with your older truck but not your 2021 Sierra.

The most likely trouble spot is the main ground where the trailer connector grounds to the trailer frame. This can usually be found on the trailer tongue, simply trace the white ground wire from the trailer connector to locate where it grounds to the trailer. Make sure this connection is tight, and the trailer frame where the wire is grounded isn't painted or corroded. You can improve this connection by removing the ground screw or bolt and sanding the area around the bolt or screw hole down to bar metal, reinstall the ground wire but you can install a star washer between the ground wire's ring terminal and the trailer frame. The washer will bite into the trailer tongue, providing a secure connection. Once the ground screw or bolt is reinstalled, you can protect the connection with a quick shot of rust inhibiting spray paint.

I've linked to a couple of our trailer wiring help articles which you might find useful.

expert reply by: Mike L