Troubleshooting Left Turn Signal Not Working on Trailer

Published 12/08/2017

Question:

I BOUGHT FOUR 17 INCH LED LIGHTS. TWO PER SIDE AT THE REAR OF MY TRUCK. EVERYTHING WORKS BUT THE LEFT TURN SIGNAL. RED WIRES TOGETHER. BLACK WIRES TOGETHER, WHITE WIRE GROUND. IM TRYING TO HOOK IT TO A 4 PLUG CONNECTOR. WHITE IS GRD. BLACK WIRE ON THE RIGHT SIDE TO ONE OF THE BROWN CONNECTORS, RED TO THE GREEN WIRE. ON THE LEFT SIDE BLACK WIRES TO THE OTHER BROWN CONNECTOR, RED FROM THE LEFT SIDE TO THE YELLOW WIRE. THE LEFT TURN SIGNAL WILL NOT WORK. PUT FOUR WAYS ON WORKED. WHAT IS THE PROBLEM? OH I TRIED THE LEFT SIDE LIGHT ON THE RIGHT SIDE TURN SIGNAL AND IT WORKED. ITS A NEW TRUCK ALSO. THANK YOU

asked by: Robert Y

Helpful Expert Reply:

It sounds like you have made the correct connections with the wiring from your new LED tail lights on the trailer.

I recommend turning your attention to the vehicle side, as it's likely that the issue is originating there. Check the vehicle side connector with a circuit tester like # PTW2993. Make sure you are receiving power at the left turn signal circuit on the connector while you have a buddy activate the function from inside the vehicle. If there is no power with the left turn signal activated, then there is an issue somewhere with the wiring on the vehicle or a missing/damaged fuse. You can check the owner's manual on your vehicle for the fuse locations related to trailer towing. Check to make sure all the relevant fuses are present and in good working order, simply replacing if needed.

If you are unable to resolve the issue, please let me know and I will be happy to look into this further.

expert reply by: Chris R