You know my pushers are not running normally, even when the puller fan is on. So, I've often wondered if the air pressure on the fans, while moving, was sufficient to "spin them" as I was driving, so as to make them appear to be on. But, each time I stop the car, unbuckle the belts, and quickly run around to look at them, they've stopped -- so I don't really know.
Kind of like that time I stayed up all night to see if I snored....