I think everyone has great ideas of what it does...

But why a fan clutch is more simple: Saves fuel. Running ala old american iron a fan all the time drains fuel and slows the engine heating up contributing to wear.
It's not uncommon to see an electric fan on all the time or nearly so in the summer- your running the a/c.

A large electric fan at the time these were built wasn't a cost effective option. Puller fans are more efficent than pushers if I remember correctly. With a clutch you can have a 10 -15 hp fan only when you need it.


M