I think he maybe meant at what vehicle speed the forward motion of the car will force the fan blade to turn without having any power applied to it. And I don't know the answer to that. I would think that it does freewheel though.

Good to see a post by you, Larry.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.