It was working fine few weeks ago. One day when I was driving, the air suddenly stop blowing out off the middle two vent. The vent sounds like suddenly shut. The Air (A/C) comes out okay from the side vents and top to windshield. No matter how I change the switch buttom, does not help. Any idea? Vaccume? Electrical? Where should I look for the sympton? I really love the 300D. Thanks.