When you're just driving around with the windows open, and when you park, do you leave the fan on, or do you put it on the closed position (the picture that looks like an " o " on the ac settings) I was told that its best to leave it on the on setting when you turn the car off so the vents remain open and mildew doesnt build up. Is this true, or should I be closing them when I park? Also, I know the AC sucks up power when its on.. does the fan? Thanks