Troubleshooting Left Rear Signal Light on Trailer

Question:

I have brake lights, and I have a right signal light as well. However when I plug in the left side light, it only flashes when I turn on the right side blinker. When I turn on the left side blinker I get nothing. Guessing a ground issue but Ill be danged if I can see where. Both lights are grounded to one of their mounting studs running through 1/4inch steel plate.

asked by: Tim

Expert Reply:

There are a few possible causes to the issues you are having with the left signal light on your trailer. I first recommend testing the vehicle side connector with a circuit tester like # PTW2993 with the trailer disconnected. Just make sure all of the pin locations are receiving a circuit and the functions are reading properly at the connector.

If everything checks out okay, move on to the trailer side connector. Look for any dirt or corrosion that might be preventing a secure connection with the vehicle.

As you mentioned, a likely cause is a simple ground issue. Just verify that all the main connector grounds are attached to clean and corrosion free bare metal surfaces. The light grounds also need to be made to clean metal surfaces. Running jumper wires from the light grounds to the main trailer connector may provide a better connection and resolve the issue.

If you are still unable to find a solution, please let me know and I will be happy to help you further. I have also attached a wiring troubleshooting article that you may find helpful.

expert reply by: Chris R