Trailer Hitch Wiring Harness - 4/7 Pin - accessories Contains module and harnesses to splice/connect to the factory electrical system for 4-7 pin trailer wiring Provides customer with wiring for aftermarket trailer brake controllers Not available on some Long Wheel Base Gas Vehicles. Contact your local dealer to verify compatibility. Dealer installation recommended. . Compatible with Transit 2015, 2016, 2017, 2018 Ford 7 Pin Trailer Wiring Diagram | Free Wiring Diagram Collection of ford 7 pin trailer wiring diagram. A wiring diagram is a streamlined traditional photographic depiction of an electrical circuit. It reveals the components of the circuit as simplified forms, as well as the power and also signal links in between the gadgets.