HeaterTreater stated it is too difficult to replace blend doors/actuactor motors on the later model F150's. Just installed a new product by HeaterTreator..."Universal Core Regulator" a solenoid operated open/ closed flow control valve that installs in heater lines under the hood. ( A push button controlled version of the old manual control valves) In winter push the small LED button & open the flow into the heater core, in summer, push the button, close the valve for A/C. So far works well, an relatively inexpensive fix for the dreaded blend door/actuator problem. Costs $100 bucks. Comes with instructions, small cabin mounted LED switch, wiring, hose clamps everything you need.
Installation was easy, took less than 1 hour to block actuator door, cut heater lines, run wire & hard wire into fuse box. I did have to cut the mounting ears off the plastic valve assembly in order to get it into the curve of the return hose. Hope this helps somebody else with this problem. Best regards-Larry