2012 Ford F-150 Trailer Wiring | etrailer Call 800-298-8924 to get Expert Service ordering a Trailer Wiring for your 2012 Ford F-150. Complete installation instructions and lifetime technical support on all Trailer Wiring purchases. Lowest price guarantee on accessories for your Ford F-150 and the fastest shipping available. 7-pin Plug - Wire Diagram - Ford F150 Forum Nov 30, 2007I checked my 7-pin plug (factory installed towing package on a 2005 F150) and the "backup" wire is black-pink stripe, NOT red. It goes to the CENTER contact in the plug. I confirmed it with a voltmeter. There is a "fat" white wire that goes to the contact at about 7:00 o'clock which is negative (or ground) and would be the other wire you would use.