Tested the valve - Thunk!
Had the wife sit in the car w/ A/C on, connected the valve again (no alligator clips, so I had to hold the leads with all four of my hands) and she confirmed cold air was a-blowin'. God I love this web-site!!!
So Gilly, looks like the push button unit is the culprit, but it seems like it could also be a short in one of the wires from that unit to the valve. I'm not real confident in my ability to diagnose anything electrical(I am, however, adept at replacing the batteries in my T.V. remote control), so is there a sure-fire test to eliminate the wires themselves as the problem? If it is the push-button unit, is it repairable? The one in the car now is labeled as "rebuilt", so it's been replaced before I got the car, same as the radio which sucks too. If this is not repairable, guess I'll buy a new one.

Thanks again, Gilly. And MB Doc!

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Dave
1995 C280
1999 Triumph Daytona 955I - my speed fix.
1982 300TD - Gone, but not forgotten.