Wow! Appreciate the flurry of posts and suggestions!
Viz139 I will definitely check if a "wire [got] damaged near the end and short out causing the fan to run all the time", but can't do so until I get the Mini back from the shop that is swapping in a new rear subframe for me right now (it was at the start of the 2 hour drive to the shop on Monday that I noticed the fan coming on even when the car was cold). Funnily enough, along the drive there were times when the fan wasn't running, so it certainly could be a wire bouncing around and shorting out to ground.
Thank you especially to Super6al for the detailed instructions on examining (and possibly fixing) the existing switch. I'll do that before I spend £60 to buy a new one. Thanks also for posting a photo of the connectors over here in another thread.
And now that I really think back on it, there might have been two days in the previous week when I was just moving the Mini for alternate sides street cleaning that it might have come on just by turning the ignition key and not even starting the engine... Those days were REALLY cold, so maybe "extremes" of temperature, either cold or hot, play a role in this switch behaving unexpectedly, perhaps causing it to "stick ON" if it was in that position when I last parked the Mini.
THANK YOU TO ALL THE POSTERS! I'm pretty certain now, having pieced together all the feedback from everyone that for my '91 HIF44 Carb'd Mainstream Cooper that I am looking at the YWL10010 8mm fan switch. I'll include a photo from MY Mini itself when I get it back to finally put the debate about what this switch is, but the photos below that I found on the web might help in the meantime.
by the way, https://www.somerfor...an-cooper-90-92 seems to have the lowest non-VAT price of £44 for the YWL10010. It's pretty inexpensive to get it to the USA using their "Small Parcel World Zone 3 - Tracked (MP1)" shipping option of £14, and that even offers £50 lost/damaged-in-shipping insurance coverage (note that they have even cheaper £7 Royal Mail options, but going from Europe to the USA, I'd prefer tracked and insured).
WEB PHOTOS:
Here's a photo where the sensor screw-in hole is in the front of sandwich plate on top of a cylinder head, pointing forward towards the grill (that would be under the black "Mini Cooper" embossed plastic air intake snorkel that runs side-to-side over the valve cover in my Mini)
Here are three other images of the YWL10010 oriented to the sandwich plate:
Image #1 Image #2 Image #3
And finally the image from Minispares with "tell-tale" text regarding use case and compatibility
ONCE AGAIN: A GREAT MANY THANKS TO ALL THE FOLKS WHO TOOK THE TIME TO POST AND SHARE THEIR KNOWLEDGE!
I'M VERY GRATEFUL!
Jim
PS: I finally found another thread about this by searching for the part number and so I'm cross-referencing it for future searchers.
