Viscous Fan

[Simonic]

My 71 is fitted with the Chrysler viscous fan.
How do i check if it's locking up at hi temp please ?
Thank You Gentlemen

[John_Kunkel]

You can't. All the homespun clutch tests are useless. If in doubt, the FSM says "replace with a known good unit".

[justcruisin]

I agree, it is impossible to check if it is driving properly at temp, the only thing you can do is with a cold engine, spin the fan as fast as you can by hand in the direction of normal travel, there should be a degree or resistance, keep turning fast until it frees up and spins easy. Remove the spring from the front of the clutch (if it has a spring) and turn the valve manually, spin the fan as you did before, if it is working the resistance will not change. However, this does not tell you if its is fully locking up nor does it tell you at what temp it is locking up, also if you are not familiar with how it should be that is a problem. Some say you can hear the fan roar on start up, iv'e never heard it roar on my Charger, although I can on my truck with its plastic fan. Probably best just to replace it.

[Simonic]

Thank You both gentlemen for your replies . My fan is the type with the spring on the front . It looks in good order and fairly new,and i have to say i've not got any overheating problems.
I was cahnging the water pump out yesterday and while i had the fan in my hand i simply thought 'how do i check this?' Hence my question.
Thanks again gentlemen