I could be wrong here,but the 7 wire connector I THINK is actually for a Power Brake booster for a large trailer.
Could be?
My 01 F150 keeps blowing fuse #19 as soon as I hook up a trailer and use the right turn signal.
You have a short circuit in the right brake/turn signal circuit (green wire)
on the trailer. Might be a corroded/shorted bulb in the tail lamp housing) or a chafed wire along the trailer chassis. If the wiring goes through the frame rail, check those points first as trailer manufacturers often neglect to install insulating bushings.