Electric radiator fan free-wheel speed...at speed

[Terry Oxandale]

Has anybody got any experience or knowledge of what is happening to a typical electric radiator fan while the car is being driven at high speed? My concern is the un-powered fan speed, being driven by the flow of air through a well-sealed radiator, and if that speed would exceed the manufacturers design and become damaged or damage something. I'm wondering if I need to remove the fans prior to a track day (which would save some weight), or if I can simply leave them on the shroud and not worry about it.

 

[Randy V]

I've had dual 12" fans on my SCCA Camaro running in A/S at 160 mph without any troubles with the fans... However, I did have some ignition system problems until I put the fans on a relay. Running them through a HD SPST switch, I turned the fans on just after taking the checkers on the straight-Away at about 150 MPH so they would be on during the cool down lap. My ignition system started cutting out (Mallory Uni-Light) then suddenly stopped altogether and I had to be flat-towed to the scales post race.. Long story short - those fans made GREAT generators and put HUGE dirty voltage on the 12v buss... I wish I would have found that problem before I nuked the second ignition module... ((Sigh))...

 

[Terry Oxandale]

Thanks Randy. That was my other concern in noticing the voltage rise on the system once the motors started acting like generators. But that was only a secondary observation by pure chance, so your note is very applicable.