It has a bi-metal spring like on a choke which causes
a viscous clutch to lock up the fan to the pulley as
it heats up.
Well, you should be able to turn the fan with the
motor off. It shouldn't be real hard, but still have
some fluid resistance to it.
Once running it will lag behind the pulley, then when
it couples up completely, the pitch of it's sound
will change and you'll feel a stronger air flow.
With it off the car (keep it in the installed
position as the silicone fluid may leak out), I
suppose you could chuck it into a vise and gently
heat the spring with a torch while turning it to see
if it engages.
GM
----- Original Message -----
> How exactly does the fan clutch work?
> What is its purpose?
> how can you check if it is operating correctly?
>
> Thanks Jon.
>
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