Picked it up at the shop today, it was just the A/C relay going crazy over the extreme temperatures we're having. There actually is an auxiliary circuit to keep the fan running even when the primary gives up, and that's the one that had gone bad.

The folks at the shop also took care of a couple extra gremlins for me, free of charge, because they had lots of questions about the car, how long I've owned it and how it's been kept in shape for 18 years. I think my car got another couple fans :p