From other postings, I thought it was the climate control unit gone bad. I bought one used (same 9452369 part number) and put it in today.
Applied battery power and the fan came right on again. Took it for a 15-minute test drive, no difference.
Removed the negative cable and pulled the climate control unit.
Then I had the idea of putting the negative cable back on and, much to my chagrin, the fan is blowing again.

With a large hole in the dash where the climate control unit should be. Needless to say, the negative cable is disconnected now.
What the hello is going on with this? Worse, what is it going to take to fix it?
I need to keep the car on the road; any suggestions are greatly appreciated!
Donald