Troubleshooting Horse Trailer Wiring

Updated 11/12/2015 | Published 11/11/2015

Question:

I have a 93 model horse trailer with red/brown and green/ yellow /brown wires coming from it and I need to connect to a 7 prong truck harness with a white black brown green yellow and red wire. I have gotten everything to work except the running lights what is my problem??

asked by: Chase

Helpful Expert Reply:

The first step I would take is to verify that the truck is sending a running light signal to the trailer. Try using a circuit tester, like part # PTW2993, and test the 11 o'clock pin in the truck's 7-way socket with the headlights on. If there is no power there, then we know the issue is on the truck such as a blown fuse or faulty wiring.

If the truck is okay, make sure the wires are routed properly on the trailer. I would not rely solely on color as the determining factor for wire function as there is no industry standard wire color code for horse trailers. I have attached a diagram that shows how a trailer end 7-way connector should be wired.

You should be able to trace each of your wires along your trailer to make sure they were run properly.

If the wires were ran properly, then there could be a ground issue on the trailer. Inspect the main trailer ground and the ground for each light to make sure there is no rust or corrosion that could cause a problem and repair or replace as necessary. You could also try running all of the light ground back to the main trailer ground.

If you cannot find a solution or the problem after following these steps, let me know what you come up with and we can do further troubleshooting.

expert reply by: Jackie C