On my 2010 F150 Truck it is labeled TRAILER TOW in the main fuse panel near the radiator for the 12V lead on the 7-way connector... It also has a black relay that plugs into it as well... There was an unmarked envelop in the glove when I got the truck and dealership told me to install the fuse and the black relay in the front main fuse panel... Has to do with trailer tow I guess???? The relay clicks when I turn on the ignition key??? I think all of my trailer safety lights stay ON whether the truck key is ON or OFF so I have no idea what the relay is for... Maybe the relay just kills the 12V lead in the 7-way connector when the ignition key is OFF...
I also have a fuse panel on the firewall on the motor side and yet another one inside the truck in the passenger side kick panel...
I think one of those fuse panels has a fuse for each of the 7-blades and 4-pin tow connector leads on the rear of the truck. My truck has the tow package...

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Roy Ken
