Trailer Running Lights Not Working on 2010 Ford King Ranch

Question:

How can I check and fix this problem on the truck itself? No power on running lights 7 pin harness on 2010 Ford King Ranch Thanks,

asked by: Louis T

Expert Reply:

I found an online copy of the owners manual which shows there is a fuse and relay that protects the trailer running lamp circuit. The relay is in position # 6, and the fuse is in position # 31. Check the fuse and replace if needed. It is difficult to test a relay, but you can remove it and swap out an adjacent relay to see if it fixes the problem. If you find a bad fuse you will want to check the trailer wiring to locate and repair the short, or you will continue to blow fuses. You will want to check the owners manual to verify these fuse locations.

The next thing to check is the trailer connector on the truck for signs of broken pins, or wires, or signs of corrosion.

If the harness you have installed is a plug and play, you can unhook the connector on the back of the harness and then test the vehicle side connector for the functions. If you do not have current there, you will want to find where the harness is plugged. unplug the harness and check the vehicle side of that connection as well. If you are getting current on the vehicle side of that harness, I would recommend the Tow Ready Custom Fit Vehicle Wiring, part # 74682. This includes the harness that plugs into the vehicle connector, and also includes the connector you mount to the rear on the bumper.

If you are still not getting any current on the factory harness, and the fuses check out oklay, I would suggest you have a trusted mechanic or your dealer find the source of the issue, as the problem is most likely be in the vehicle wiring.

expert reply by: Jeffrey L