Troubleshooting Factory Trailer Wiring for 2003 Ford F250

Updated 12/03/2014 | Published 12/02/2014

Question:

The 7 spade plug on the truck I get clearance lights to work. The turn lights and brake dont work. I check the factory plug and the only thing I can get is power and clearance. Where might my problem be if not getting any turn or brake out of the factory connector?

asked by: Jason

Expert Reply:

First I recommend cleaning the connector and make sure there is no corrosion on the pins. Check the wires at the back of the plug. You may need to remove the wires from the connector as corrosion can build up in the connector. If all of the connection points are corrosion free, then begin testing the wires themselves.

Since you are not receiving a signal on some of the pins I recommend tracing those wires back till you find a point where the signal is active. It may be that connection points between the wiring harness and the vehicle wiring are bad.

I would also recommend checking for any blown fuses if you have the tow package. I have attached a wiring article for you to review while troubleshooting your wiring harness.

I would also recommend checking the ground connections on trailer for the lights and trailer connector and the ground connection point on the vehicle wiring harness. Faulty ground connections can cause different issues with trailer lighting.

expert reply by: Chris O