Troubleshooting Fuse Blowing and Wiring Heating Up for Left Side Lights on Trailer

Updated 04/08/2022 | Published 04/03/2022

Question:

I just wired a trailer and it keeps blowing the fuse for the left turn signal/brake light. The wires for the left lights get pretty hot as well. The right turn signal/brake light and marker lights on both sides work great, its just the left side. The wire harness is new and I dont see any cut or open wires making contact with the trailer. I removed the paint from the trailer where the ground wire is connected to the trailer for a good metal to metal contact. When I install a new fuse in the truck, the left turn signal/brake light works for a few seconds but is very faint, and then stops working. The running lights on the left side work the whole time, its just the turn signal/brake light. I cant seem to figure out why its doing this. Any ideas? Do you think I have a bad ground somewhere?

asked by: Bill

Helpful Expert Reply:

It is likely that you have a short in the wiring. Although, it is always a good idea to check your other ground connections. Since it is a new wiring harness that is probably not the problem.

Start by checking your 7-way using a circuit tester like the # PTW2993. It would also be a good idea to clean your 7-way connections while you're at it since corrosion and debris can cause problems.

If everything checks out for the left side lights then it is a problem on the trailer. If it doesn't then the problem is on the vehicle side. Whether it is the trailer or the vehicle, work your way along with the circuit tester to isolate the problem and fix the short.

expert reply by: Robin H