Thanks for the reply, PigLick. This is a stumper for the common man, isn't it? There's a MINI tech out there somewhere who's thinking "Duh!"
For about three weeks leading up to Helen Blaze's Day, the AC would stop while the engine idled, but not consistently. Usually, I could short-term fix the problem by simply pressing the power button off then on again. I never suspected anything other than an AC problem. The temp gauge always read normal.
When the temp did eventually spike, it spiked quickly, within maybe one minute from normal to nuclear. It was that road trip on a warm day, followed by extended idling that got things nice and toasty under the bonnet.
Here's the monkey wrench: That blown fuse affected the AC and the engine temp,
but not the power steering.
If the PS works just fine when it gets hot, then why does it need a fan? And if the PS does get hot with a disabled fan, then why does the AC fail? And should we be motoring knowing that the PS, AC and engine cooling systems could all be brought down by a stray sandwich bag?
To summarize: What's up with that?