The good news is the windshield wipers are now working. The 64 thousand dollar question is how? With my 42+ years of Volvo experience, this is indeed strange.
This morning I fired up the garage woodstove, expecting a full day of diagnostics and frusuration. I had already located several sources for a rebuilt wiper motor, but this would delay the repair until later this week.
With the inside temperature still around +5C, I lifted the upper fuse tray and removed the 30 amp fuse. Before figuring how to get at the wiper motor, I decided to swap 30 amp fuses and see if there was any change in the symptoms. F9 is indeed a fuse; Cooper Bussman low-profile, slow-blow:

I once again did the resistance continuity check and it appeared fine, but I did replace it with the identical fuse for the starter motor (F34) in the upper fuse tray. I re-installed the fuse tray, then tried the wipers and they worked. I installed the original wiper fuse into the starter motor fuse location, fully expecting the car to not start, but to my utter surprise it did start and the wipers still are working. Strange eh?
I still don't know if somehow the wiper motor module reset itself, is damaged or the wiper motor itself will fail in the future. I'm a bit suspicious that even a Volvo has not evolved to the point it can self-repair, so I fully expect I have not seen the last of this apparent serious problem. I'll buy extra 30 amp fuses, just in case.
Any comments or ideas?
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