7-Way Trailer Wiring Harness not Working on 2011 Ford F-350

Question:

My 7 blade plug on mt 2011 f350 is not working. I have no lights blinkers nothing. All the fuses are good and it is wired correctly. Is there anything else that I can check?

asked by: Benjamin H

Expert Reply:

There are a number of possible issues for why the 7-way on your 2011 Ford F-350 may not be working, and I'll go over some things you can check.

You started off well by checking the fuses, but since those are good you will need to determine the specific problem by using a circuit tester if you do not have one - like the very handy Cordless Circuit Tester # PTW2979 - and test the connector on your vehicle after disconnecting it from your trailer. Use the tester to check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals; if not then the issue is with the vehicle wiring. That can be problematic because tracing or finding wires on the truck side is really difficult, as the cause would be a short and damaged wiring, so that may require a trip to the local Ford dealer or a mechanic if you can't find the wires that are damaged and repair them.

However, if the signals going into your truck's harness are okay, you'll need to test the signals coming out of the harness, and if they are correct then your issue is likely going to be with the trailer side wiring so you will want to check it for broken, crimped, or damaged wiring. You will also want to check both your vehicle and trailer connectors for corrosion, which can be green or white in color.

A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you are going to need to replace the plug with # H20043 for the trailer side or for your F-350 the Curt T-Connector Vehicle Wiring Harness for Factory Tow Package # C55774.

You'll also need to make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion. I have added links below to a pair of help articles on trailer wiring, including a troubleshooting guide for you to take a look at. Additionally, to help prevent any type of corrosion in your connector, and increase its durability and lifespan I highly recommend using Dielectric Grease for Electrical Connectors # 11755.