My heater / ac blower works fine, but when i press the recirculate air button on my 97 Caravan, the vents no longer blow air (although the blower is still on), and I could hear the air going somewhere, just not out any vent. When I turn the button off, then the vents work normally. I take it there muse be some king of electircally controlled motor somewhere that closes off fresh air, but might be sticking???