I scavenged a working motor from our old furnace a/c unit and recently installed it (and ductwork) in my basement to draw excess hot air from around our fireplace insert on the main level. Unfortunately the motor only seems to be blowing in the a/c mode which is much too fast even for pulling hot air downstairs. It has a capacitor, but what else do I need to do to run it at the lower speed. Would a manual switch work? I'm assuming an industrial type rotary control would kill the motor if the speed was too low.