Troubleshooting Trailer Turn Signals Both Flashing With Brakes or Running Lights On

Question:

Both turn signals work fine unless I have the headlights on or the brakes on. One turn light will blink brightly and the other dimly, whether Im using the right or left turn light.

asked by: Dave

Expert Reply:

It sounds like there is a ground issue in the wiring, probably on the trailer side, but it will be a good idea to check all of the grounds to make sure. Start with the white ground wire from the converter box of # 119178KIT. Make sure it is attached to a clean and corrosion free bare metal surface on the vehicle.

Next, check for any dirt or corrosion in the vehicle and trailer side connectors. You can then move on to the trailer side. Check the main ground coming from the trailer side connector. It, too, should be attached to a clean an corrosion free bare metal surface.

Next, I would check each of the lights. Trailer lights usually ground through the mounting studs. The grounds should be attached to the trailer and free of rust and corrosion. With everything properly grounded your trailer lights should work as they are supposed to.

You can also test the wiring going into and coming out of the converter of # 119178KIT using a circuit tester like # PTW2993. If the signals are correct and match, whether the lights or brakes are on, then you know there is a problem with the trailer wiring. If the signals are correct going in but wrong coming out, then there is a problem with the converter, and it will need to be replaced. If the signals going in are not correct, then you know it will need to be re-wired.

expert reply by: Michael H