I have a 1994 disco with the following problem:

First, the power windows began both working at the same time. Then, when running the blower motor for either the heater or A/C, the rear windshield wiper will come on after about three or four minutes. The only way to stop it is to turn the blower motor off. Usually the blower motor will slow radically when the rear wiper comes on or stop totally.

I believe the two issues are related because one way to kick off the rear wiper/blower motor problem is to raise or lower a window (both will operate).
I have no idea where to start. Any thoughts, comments, or suggestions greatly appreciated.

Of course, I ignored the problem until it became warm enough to use the A/C, but the season is upon us. Help!