Left Brake Light on Boat Trailer Not Working

Question:

2012 gran caravan I just bought used.wired probably by U-Haul Operates all the boat trailer lights correctly but the left brake light. Checked the vehicle pigtail and all is correct, but it does not light continuous on the left brake light. Vehicles lights are correct. I have installed two of your hitches and two of your harnesses on other vehicles in the last year. Do I write this off as a bad controller and order a new harness from you and install it or is there something else that could cause it? I notice that the controller is mounted in a terrible place that gets all the sand, dirt and salt that the rear tires throw up.

asked by: Joe M

Expert Reply:

If the turn signal is working on the left side but not the brake light, then it could be a bad ground connection. Ground problems normally show up when there is more load on a circuit like the constant 12 volt draw of the brake light.

Check the ground for the left side taillight. Many trailer lights ground through the mounting studs unless there is an obvious ground wire. In either case make sure the ground is attached to a clean and corrosion free bare metal surface. You will also want to check the main trailer connector ground and the pins on the vehicle and trailer side connectors and make sure they are clean and free of corrosion.

You can also check the vehicle side connector with a circuit tester like # PTW2993 if needed.

It could also be that the converter is bad and needs to be replaced. You can test the converter by testing the wires going in and, if they are correct, test the wires coming out. If the signals coming out are not correct, then the harness will have to be replaced. If the signals are not correct going into the converter box, then the issue is on the vehicle side, though this seems unlikely for a newer vehicle.

expert reply by: Chris O