I seem to begin a lot of "upgrade" email like this… I've been thinking about this for a while and finally pulled the trigger.
I got the wiper motor from good 'ol JC Whitney (all links below). I have a Leer 100R cap on my crew cab, long bed F350. Who wouldn't want a wiper on the back (cap) window? So here's my story;
1) The wiper motor clearing the top of the tailgate is a go-no-go deal. On my cap I drilled the hole for the wiper drive armature 2-5/8"ths above the bottom of the rear window frame. The motor then clears by a follicle of a hair, of a house of ill repute's, employee. That is a critical measurement.
2) My cap has a dome light. I grabbed 12v there and ran it down the frame of the cap door to the motor.
3) I then ran the ground lead from the wiper motor, along the cap door frame (bottom), then up to the top of the door where the hinge is and followed the other wiring (dome light, high-mounted third brake light) back down to the bed of the truck, just above the driver's side tail light. From there I ran to the dash (cab) and mounted a simple single pole/single throw switch to turn the wiper on (grounding the motor).
Thoughts after the project…
I bought a 90 degree (sweep) wiper. If the armature pin is not in the glass of the cap door and you buy a 180 degree sweep motor, you're going to be dragging the wiper blade across the frame of the cap. Simple geometry. But now that I have it all assembled, maybe the wiper blade can take it… The 90 degree sweep (the only option other then 180) only clears (cleans) a small section of the glass. But maybe that is enough. We'll see…
The wiper blade is a pretty cheese-ball deal (very flimsy). Now that it's all installed and I see how everything fits together (this is called a "suck it and see what you get" process) I think one could go the local auto parts store and buy a much better wiper.
The wiper motor is a little on the loud side, if, you have a short bed Rice Burner. Crew Cab, Long Bed Ford Diesel - no problememo'. The wiper motor is silent