Troubleshooting Trailer Wiring with Marker Lights Working But Tail Lights Will Not

Question:

I ran new wires and the side markers light up but not the tail lights. I made sure the ground is metal on metal and that the bulbs work. So Im not understanding what the problem is. Both lights go into one ground wire. Thats how the kit came. Any ideas?

asked by: Jason

Expert Reply:

Without knowing what kit you are using, I suggest trying a wire from the ground of the tail lights directly to the negative terminal of the battery. If this works, then you know you have a ground issue. If this is the case, I recommend making sure the ground connection is bare metal to metal at even the hardware of the light because they often ground through the mounting hardware. If that doesn't work, run a jump wire from the ground to the main trailer ground.

I also suggest cleaning the connections from the vehicle to the trailer on both ends making sure there is no corrosion or debris. Using a little dielectric grease like # 11755 will help with the connection to keep moisture and debris out.

You can use a circuit tester like # PTW2993 to ensure your tail light connection is getting power and there isn't a short.

If you still have issues let me know and we can continue troubleshooting.

expert reply by: Jason S