Engine off, it slows down to a stop. Power on, back again, turn the ventilation fan from Auto to Off, slows down but still there.
Realise the air conditioning is on, turn that off, it slows to no ticking. Learn, after how many years driving this car?, that the air conditioning runs the fan at Speed 1 irrespective of the fan speed selected!
Sounds like something in the fan, maybe a bearing worn or debris being knocked around, but nothing major; just bloody annoying!
In the light of day, well the light of today as I procrastinated, find it definitely is the fan which is — and here is the win — accessed by removing a single screw. No major dashboard surgery required. Pop it out, blow out with an air duster, bit of electrical safe lube spray, twist lock back in, secure with THE screw, sorted!
Bravo Fiat interior* designers!
* Not sure this makes up for the recommended — but avoided by crafty mechanics — ‘remove the engine’ instruction to change the cambelt (thanks to a long 5 cylinder transverse engine jammed in between the wheel arches)!