Rear Wiper acting wierd

2000 Montana, My rear wiper will work if I toggle the wiper button to "clean (where the washer is supposed to stream water). The wiper moves all the way to the right and back. But if I toggle the button just "on" The wiper stops in the middle of the window, consistently.
I dont see that it is the motor, since when I toggle it to clean, it moves all the way back and forth.

Any ideas?

There may be a dirty/corroded electrical connection at the motor.

It's not uncommon for water to sneak in under the rubber wiper seal and drip down on to the motor.

To inspect for this requires removal of the wiper arm nut cover, removal of the locking nut and removal of the inside hatch panel. (A couple of screws and/or "christmas tree" clips need tp be removed also)

The dirt resistance on my rear window wiper, caused my fuse to blow.

Try cleaning the window with Rainx cleaner, also look at the bottom of your thread for Simular threads.

Okay, I had not considered that possibility....I will disassemble, and clean all the contacts and see what happens. I already tried just removing the blade and lifting the wiper arm up and turning the wiper on to see if zero resistance made the difference. It behaved the same, it stopped in the middle of the window when the wiper button was pressed "on".

Had a town car, that would park the window wipers in the middle of the windshield, the root cause is a bad wiper motor.

I noticed the same problem on the Towncars, and sister cars.