Wiper won't stop--finally fixed
 

After reading and following all the posts to date to fix the problem, including adjusting the wiper stalk contacts, trying a substitute stalk and purchasing a new relay (without success), I finally removed the wiper motor and assembly. Inside the silver colored box there is a worm gear and disc bathed in dielectric grease (this mechanism shuts off the motor in the park position), and three copper contacts similar to those inside the wiper stalk. I redistributed the grease that surrounded the contacts, cleaned them with emery paper and cleaned off the disc on which the contacts ride. Problem solved. I think that the old relay probably still works, (I didn't retest it), so if someone wants one, let me know (new ones are $100).

Nice job on the fix. Maybe it will last another 100k...

It's a 78 SC--46k--still working on the first 100!

Only 46K - WOW. Mine has 200K+ and is, well, torn a part. It has been that way for 2.5 years :( Maybe in a year or so it will be driveable. Enjoy the car and drive it like it was supposed to be driven - hard...

I need to do this to my 78. How hard was it to get the wiper motor assembly out? Do you have to unbuild half the car?

Basically need to remove the air plenum and then the wiper assembly in total. Removing the wipers is straightforward, but you need a 22mm wrench or spanner to get the nuts off. Then you can service the motor assembly without removing it from the wiper drive assembly. You need to remove the clock and tach gauges to get access to the two bolts that hold the assembly in place. Also need to remove the wires (keep track of which color where). The Bentley manual has some pictures, but they aren't really necessary.

OK, so the "final" fix I described wasn't final. Not long after, the wiper again failed to stop and sometimes started on its own. I took apart the gear mechanism on the motor again and discovered two small pits, one on each side of the metal tab in the center of the circular metal plate on top of the white plastic gear. The innermost of the three copper contacts on the lid to the gear mechanism makes contact with the metal tab and breaks the circuit, stopping the motor. The pits eventually build up and reduce the effective contact width of the tab. The momentum of the wiper moves the copper contact across the tab and it "skips" across the tab instead of stopping on top of it. The solution was to remove the plastic gear (have to remove the center nut connecting the wiper motor to the wiper arm mechanism to release the plastic gear). Then bend the three tabs on the underside of the white gear to release the metal circular contact plate. I used a Dremel to remove the pits and smooth the surface of the tab, then finished off with emery paper. Then reassemble. Be careful of how you position the motor onto the mechanism (don't move the mechanism arm from the original position), or you may end up reversing the park position of the wipers to the passenger side instead of the driver side. Don't ask how I know.