Troubleshooting Trailer Wring Problem on Trailer towed by 2000 Ford F250  

Question:

Expert Reply:

The first thing you'll want to do is determine if the problem lies with the vehicle or trailer. Use a circuit tester like part # PTW2993 to test each pin on the trailer connector as its function is activated. I've linked you to an FAQ article that shows what the function of each pin is.

If the trailer connector isn't showing power, keep in mind that there can be more than one fuse box on a vehicle. The main box under the hood usually has the tow package fuses, but on certain models of Ford Trucks, the trailer light fuses were in a smaller fuse box on the firewall. Your owner's manual should have more information about this. You might also have a bad relay. Use your owner's manual to locate which relays are related to the trailer tow package wiring. Try swapping out adjacent relays to see if this fixes the problem, as you usually can't tell a relay is bad by looking at it.

If the connector on the vehicle or trailer is damaged or corroded, you might need to clean or replace the connector. Corrosion can prevent the signals from passing from the vehicle to the trailer, and could prevent the trailer taillights from working.

If everything on the vehicle checks out okay, the problem is in the wiring on the trailer. Beginning with the connector, trace the wiring rearwards looking for loose connections and pinched or broken wires. Make sure the white ground wire from the trailer connector is securely attached to the trailer frame, usually on the trailer tongue.

Make sure the lamps themselves are properly grounded either through their mounting hardware being in contact with the trailer frame or by a separate ground wire.

I've linked you to a trailer wiring troubleshooting FAQ article that should be helpful.

expert reply by: Mike L

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