Auxiliary cooling fan death/rebirth
I am not exactly sure the function ...but it did not work. The motor ran but the fan blade was stationary. My mechanic did not have the time, so in my 'what-it-is' fashion I replaced it.
It turns out the shaft had a horizontal pin like the crossing of at lower case T to drive the blade. The original longer exists (see red arrow) so there was no drive. (I am not sure what had been on the frontend of the blade - nothing when it came out.)
The OEM P/N gets you a runaround. But, Amazon has warehouses of perfectly suitable substitutes for, I suspect, a fraction of the original list ...$34.
It fits flush in nearly the same footprint (it is the same blade size) as the OEM. It took me about 2 hours because I had to stop and think a lot.