I have a 1996 GMC Jimmy SLT and I have a problem with the rear winshield wiper. it does not work, it makes noise when the switch is pushed but does not move. what could be the problem and how would I repair this. please help.
Take the rear hatch apart (screws, spring clips, inner panel screws (12), etc) to get to the wiper motor. Upon close investigation, the gear box attached to the motor can be opened up. The motor obviously works since it chatters so something else is not working, makes sense.
Opened up the gear box, the motor shaft drives a worm drive gear (plastic) that meshes with a gear wheel (plastic) that has an eccentric cam (metal) on the gear wheel that attaches to a metal arm that meshes with another metal gear arm that is attached to a long shaft that passes through the hatch door and terminates with the finely splines end of the shaft (where the wiper attaches to). As the eccentric cam turns around the gear wheel, the metal arm moves back and forth thus creating the wiper effect. Lot of action in a small space, pretty cool actually).
My basic philosophy is that if something can be assembled, it should be able to be DIS-ASSEMBLED (in theory anyway). So fiddling with the thing eventually led me to the conclusion that if I put the wiper nut on the end of the wiper shaft and gently tapped the nut I could drive the wiper shaft (and its metal gears and arms back out through the metal housing (Oh, forgot to say that if the wiper shaft was "rusted" in its sleeve and would not oscillate back and forth). At the end of the shaft (on the outside of the vehicle) there is a metal "washer" that was an incredibly tight fit (this washer holds the shaft from falling into the gear box) so you have to keep tapping on the end of the shaft to eventually drive the shaft past this holding washer.
Once you get past the washer the shaft would not pass through its guide sleeve in the metal housing (remember, "rusted" in place, seized). Tap it out with a Phillips screwdriver acting as a long punch. Then cleaned the interior sleeve by reaming it with a long circular steel brush (3/8" diameter brush that is designed to clean out push rod holes) and polished the wiper shaft with fine sandpaper, then lubed and reassembled the whole smash making sure the wiper shaft now moves freely in its sleeve. Put it all back together in the vehicle and we'll see if it works. Fingers crossed and if it works, "say wow Molson"
