For what it's worth, my power mirrors didn't work when I purchased my van.
However, after replacing my driver's side window regulator this summer, they
came back to life.

The reason? I disconnected everything in the door while disassembling it and
gave all the contacts a cleaning. After re-assembling the door, I tried the
power mirror switch and heard the motor straining. I gave each mirror a push
to get it started and since then, they've worked. As a matter of fact, they
get smoother the more I used move them. They probably sat in one position for
years. Defrosters work much better now, too.

Paolo
89 Carat 154K