The controller for that unit is hooked to the steering column just behind the dash panel (metal plate) directly under the column.
It sounds stupid, but when was the last time you changed your wiper blades?? Old blades will stick to the windshield and make these unit do some really strange things. (Like stop for a few minutes after running for an hour, not stopping in the right spot, etc...) Also, binding linkage can cause problems.
The OEM manual has about 5-10 pages on diagnosing the wiper problems. I'll look in mine tonight and see if I see anything that matches your described problems.