Well im hving this issue i took a trip to LA and while i was driving i had to keep turnibg on the heater because it kept getting cold in the car. While driving i noticed air was coming from the defrost vent and both side vents. When i turn the cold air on the defrost flaps close and the center vents open and when i turn the heat up the defrost opens again i know that is working correct its just when i have it turned off on the O air leaks. i drove my friend 1992 300e and his does not leak what should i check. Is it the vacum distributer which is behind the glove book on the side which makes the pods open and close?