a fan clutch is to spin the blade by hand with the engine stone cold and not running (of course), the fan blade should spin freely. If it doesn't then the clutch is bad...to be sure run the car around until the motor is completely warmed up and then turn the car off and try to spin the fan again, there should be considerable resistance compared to the cold start test...if seems the same then it's same problem...clutch is bad..I gotta tell you though, I have never ever seen a fan clutch go bad to the point of causing cooling issues.....

Which one is it?

When spinning it dead cold, it only spins about 1/4 of a turn. It definitely is not free spinning. Quite some resistance.

I bought a used working fan coupling either way(Seller showed video of it working and it is only 2 years old), but just curious as to the correct test procedure.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Sounds like it is probably still good. Does the fan clutch engage with a roar when you first start the engine (and for the next 20 sec or so)? Does the car temp stay relatively stable when idling? If all of the above are true then your clutch is probably in good shape.

I spun it again with a lot more force this time and I got it 5/6 of a turn...Not quite one full rotation, but close.

Temperature stays OK when idling, but it does not roar at all -- ever not even first start. I thought it was strange when I first got the car because of it, but I thought it was because the cooling system was OK...but now ever since the scary stuck in traffic red line event, I need it to be functional.

My aux fan does not engage either, but I'll tackle that once the VFC is functional.

__________________
2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k