The smell that comes in on a warm day when I try and use only the air vent for cool air to come in, smells like a musty odor, we put in new passenger air filter, sprayed the vents with special spray for such problems in cars and altho it did lessen the odor it still faintly comes thru. The smell does not come in when I use the heater on or the air conditioner on only when I try to use the basic vent with the heat turned off.