Troubleshooting 7-Way Wiring on 2014 Ford F-150

Question:

I have a 1999 SandH 3 horse trailer. The running lights work with my truck 2014 F150 with both tail lights, but only the left tail light has blinkers, brake lights, and hazard lights. I hooked my 7 pin connecter to 2 separate trucks, one Toyota and one Dodge, and everything worked on both tail lights except the running lights on both tail lights. Everything pretty much swapped and none of us can figure out why its doing it.

asked by: Jade C

Expert Reply:

There's a bunch of possible reasons this could be happening on your 2014 Ford F-150 and I'll give you some troubleshooting steps. The first thing to do is take a look at your owner's manual to locate any fuses or relays and ensure they are all there and in working order. If they are, in order to determine the specific problem you will need to purchase a circuit tester like # PTW2979 and test the connector on your vehicle after disconnecting it from your trailer.

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. If the signals going to your 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.

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 # 74682 for your F-150.

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 a link below to a help article on trailer wiring for you to take a look at which may also be of use. 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.