first off what year is it? take the door panel off and use a multimeter to test voltage at the motor harness to see if it's getting power when the switch is activated. if it's getting power then it the motor, if not then it's probably the switch itself. I had the switch go out on my 03 when I had it.
2013 F150 4x4 SCrew XLT 5.0L
Midwest Crew #22
Official FocusFest Event Planner