Trailer Running Lights Work But No Brake Lights or Turn Signals

Question:

Every thing seem to go flawlessly seemed very simple but I now have no turn signal or brake likes just running lights on the trailer. Do you know what the heck might be wrong?

asked by: Brad

Expert Reply:

Optronics trailer tail light # ST5RB grounds through the mounting studs. If it is attached to aluminum or there is something in between the light and where it is mounted then that can interrupt the ground.

Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. Like I mentioned before, if there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

You can also check the vehicle side trailer connector to make sure you are getting brake light and turn signal functions on its connector using a circuit tester such as # PTW2993. I have included a link to a video showing how a circuit tester works.

expert reply by: Michael H