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Old 03-09-2021, 10:42 AM   #2 (permalink)
Somewhat crazed
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My understanding is the fans are driven on by a temperature sensor somewhere in or near the peak temperature spot in the cooling system. Ditto for multi-speed. When you have the A/C on you are dumping hot air into the cooling systems input effectively making it a very hot summer day. My golf reduces engine power if it gets too hot after measuring intake temps. If you think there's a benefit to killing the fan, just disconnect one at the fanhousing power connector and measure the change. Those connections are made to come apart.

On the other hand the F250 fan mostly idles,BUT it has 8 gallons of coolant and is overcooled for most operations below 1/2 throttle
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