I'll try this again... I wrote out a 10 minute detailed explanation, and closed the window without hitting "post."
Anyway,
My wiper motors were both non-functional, (a) did not move in either direction, and (b) would move in one direction only.
Unit A:
I verified air supply and with no pressure, worked the lever back and forth with no problems.
I then pressed the red bypass button and tried the unit with no response.
Injected a squirt of air-tool oil into the intake port and tried again... the wiper moved to the end of it's arc and stopped locked in place.
I then disconnected the lines and fely for air movement as I worked it back and forth, no air was coming in or out of the "exhaust" port pipe.
With a my Leatherman, I wiggled the pipe out of the port and saw it was packed with mud/sand... almost like a wasp nest or termite tube. I cleaned that out and retested... no change. but when i moved it manually, I could feel air pump in and out of the exhaust port.
I filled the tube with oil and put it on at the top of the "suck" stroke to pull it into the motor... then worked it by hand for a minute.
Hooked the airline back up and gave her pressure... she moved and stopped... then "*chunk* and the red button poped back out and she moved back slowly..*chunk* and slowly started working again... all the while puking excess oil and dirt.
Unit B worked in one direction to begin with, so it was just a matter of getting the oil in there and working it manually, then hooked up. The more they ran, the better they ran.
This seems to be the standard story with these. They sit and get fouled with old lube or debris and just need a good lube and cleaning out. Hope it helps,
Heath