Haven't attempted reversing polarity, however, observed the auxiliary fan in motion. The fan rotates clockwise as you observe it from standing in front facing the motor. Too tight to get my hand in there to feel for any air movement. Once again detected a decent volume of air blowing out and not sucking in. The blades appeared to be the same pitch as the primary fan which indicates to me the air should be getting sucked in through the radiator and not reverse. Hope to reverse polarity tomorrow.