The motor stops with the wiper CCW (drivers side about 10:00). The voltge is good. Switching function is correct. Diode on the wiper motor is OK. Wiper relay is OK (new).

Are these known to fail like this? The internal switch seems to be under the nylon drive gear. Doesn't look easy, but could press it apart.

 

Extra details...
Although I've owned it for a while, I'm just getting around to sorting out a few of the gremlins. The wiper has NEVER worked. Broken wire in the "Body to Liftgate" harness. No doubt fatigued from 30+ years of opening and closing. That has been mended. The wiper motor runs and parks. Just in the wrong place. Also, the wiper motor is from 2/10/2006 (Mopar) R4856364 so maybe its is for the wrong application. ???

 

Working now. A bit grouchy to get apart. I had to drive the pressed spline out of the output shaft - carefully! The culprit was the rotary switch contacts on the underside of the driven gear.
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This all started with dead instrument lights. That lead to the fuse box rebuild (broken fuse clips) and the dash coming out. All light bulbs serviced in there. Dome and map lights, check. Rear dome light, check. Finally the Body to Liftgate harness and rear wiper. It will feel really good when it is all buttoned back up.

 

 

Be sure to replace the shaft seal o-ring

 

No o-ring on this one. This one has a profiled seal with a lip. The output shaft hadn't leaked and I just pressed it back snug. My take was heat that cooked the lube or oxidized something that built up on the contact. The Jeep is from the AMC era, the motor is Mopar 2006. IDK.