Troubleshooting Running Light Circuit on Trailer Pulled by 2001 Ford Expedition

Updated 03/26/2013 | Published 03/23/2013

Question:

My trailer lights tail lights worked a few weeks ago and have gone out. I have tested and found there is no voltage at the Exp pulg. I was looking for voltage on the brown wire. The blinkers on the trailer work ok.

asked by: Mike W

Expert Reply:

If you have tested and are getting voltage at the trailer connector when the brake lights and turn signals are activated, you most likely have a blown fuse.

Check the fuse box under the hood. The box should have a legend on the underside of the lid that identifies the circuits, or you can check your owners manual for the proper fuse location. Keep in mind that on some Ford trucks and SUVs, the fuses for the tow package are located in a separate fuse block mounted on the firewall in the engine compartment.

Before replacing the fuse, you will need to locate and repair the short circuit that caused the fuse to blow. Closely examine the running light circuit on your trailer, which is typically the brown wire. Look for broken or cracked wire insulation or loose wires that might have allowed the copper conductor of the wire to short out to the trailer frame. Also examine the trailer connector on the vehicle and on the trailer, and make sure it is not damaged or corroded. Once you find the damaged portion of the circuit and repair it, then you can replace the fuse.

I have linked you to some wiring troubleshooting FAQ articles that you might find helpful. If you cannot find a blown fuse, please let me know and we will look into some other possibilities.

expert reply by: Mike L