Correct Viscous Fan Operation

I'm getting things ready for my 340 rebuild and am making a list of parts to get. I was wondering if I need to replace my viscous fan or not. Is there a way to determine if it is ok? If I don't need to replace it, I can use money for more important parts since it is are round $130. for a new one. The car is in storage now and it's about 18 degrees outside. I can turn the fan fairly easy, there is some resistance but it does turn. So it this considered ok?
thanks,

If you give it a spin and it turns more than one revolution its time to replace. Or if you can wobble the fan on the shaft its time to replace. Or if its leaking its time to replace.

BTW, you can get the clutch unit for a viscous fan at any parts store. A non thermal unit will be about $35 and the thermostatic ones are about $50.

Well this helps because a cannot get it to turn that many times by itself. I can turn it freely with just one hand.So it sounds like mine is ok.Thanks for the tip on getting a replacement unit at parts store this helps also.