I just fixed mine today. It was clicking but no movement.

1. Removed rear wiper arm.
2. Pulled motor assembly.
3. Sprayed down splined shaft with WD-40.
4. Removed black plastic cover from gearbox.
5. Turned motor shaft with a screwdriver until things broke free. Proceeded to flush with WD-40 and turn motor shaft with my finger.
6. Connect power to motor, and jumper rear window switch as well as lock.
7. Run motor and assist with pliars if needed while continuing to lubricate.

Motor took off and ran free after that. It did not appear that the gearbox could be disassembled, so no real fix could be performed unfortunately. However if there was a way to resolve the fact that steel and aluminum do not like each-other under corrosive road-salt conditions things would be fine.

 

I just fixed mine from a 97 Blazer after going through 3 pick a part motors I went out and bought a reman from a parts house for $78.00.

What I see is two things going on in the motor. The shaft that goes through the gate will seize and strip the worm drive gear in the motor AND I would suspect that people that chose not to clear snow and ice from the rear hatch area will turn the wiper on and strip the gear.

A good way to tell is turn the wiper on with the gate and hatch CLOSED (the saftey switch prevents wiper from activating unless all are closed and latched) and if you hear the motor running pull up on the wiper. If the gear is stripped it will start working UNTIL it goes to park again where the stripped section of the gear is.

The pulse modulator being bad will prevent the motor from coming on at all. It is the black box attached to the motor bracket.