I've owned my Expy for two years and the wiper hasn't worked until today!!! Here's what I did. in write up form.(i should have taken photos!!
Remove gate trim and verify that motor is trying to work.
If it is, you can repair it. if not it may be junk or a blown fuse-diagnose
Repair Procedure:
Remove wiper motor assembly and remove mouting bracket.
Take rear cover off motor
Use a torch and apply a small amount of heat to the shaft housing to loosen up the corrosion in the shaft. Let cool slightly.
reinstall wiper arm retaining nut.
On a block of wood, tap the wiper arm retaining bolt until you see the shaft start to move and the gear coming up out of the housing. It may take 6 or so good hits.
Sand the shaft with some 200gr paper to remove the corrosion(which is why it won't work)
Take a drill bit that is the same size as the hole in the housing (5/16+- iirc) to remove the corrosion in the housing. clean housing with some air.
Ensure that the gear and shaft will turn easily in the housing (install backwards and turn it) the shaft should not bind at all. if it does, do sandpaper and drill procedure again.
Apply lithium grease to the shaft and put some in the housing.
Reassemble, connect power and test.
Reinstall motor, wiper arm and test. It should work fine and save you a bunch of $$$$ you can use for gas!!!
Time to do 90 minutes since you know what to do. It took my son and I a couple hours to get it as we were going slow and reassembled the whole thing about 3 times to test our efforts.
Merry CHRISTmas everyone!!