from under seats the heat trickles out....not sure if vent or just comming from front floor. the center air vent only swings right or left; bumber you can't just face it up towords headliner. Yes, your right I should be able to completely close that vent but...Germans....used a pully cable system for that trap door, I can't get to it as to tighten that cable so it will close all the way, Hey, there is only so much my bobbie pin, nail file and a butter knife can fix!! I suppose I should find me a nice Mercedes man.