Troubleshooting Trailer Lights That Are Always On

Question:

My trailer lights are acting funny. When the headlights are off, the brake and turn signals work but dim, acting like the running light. When the headlights are on, the lights come on as bright/brake. Once the headlights are on then nothing else functionally work. The turn/brake lights dont change. I think this is because the brightest lights are already on. I have checked ground and proper connections to the wires.

asked by: Jason H

Expert Reply:

Start off by checking the connector on both your tow vehicle and your trailer. Look for debris or corrosion and clean as necessary. I know you said you checked the ground, but I just want to make sure that you have checked the ground wire on all of your trailer lights. They need to be secure and connected to a clean, bare-metal surface.

If you have checked all of that and it looks good, I would try testing the connector on your vehicle with a tester like part # PTW2993. Make sure that all of the functions are working properly because there could be a ground issue or loose wires on your trailer. A sure way to know which end the problem is on is to connect your trailer to another vehicle. If you are getting the same problems, then the issue is definitely on your trailer.

After checking the grounds, the only other things would be if your wiring is messed up or if you changed your trailer lights to LED. Since LED lights don't require as much power that could be why they are showing all of the time. If this checks out too then the only other thing would be for you to take your towing setup to a local trailer shop and have them inspect everything physically.

I have linked a helpful article on wiring that you can reference as well.

expert reply by: Jon G