You have a broken rod that operates the flap that opens and closes to alow/stop fresh air comming in, it is located under the glove box, stick your head under the dash on the passanger side (under glove box) and look for a plastic box with a (same size as your hand) square opening, the flap you can feel with your hand, you can move it open and shut with your hand, unfortunately the rod that operates that flap is located on the outside of that plastic box towards the kick pad and computer, you cannot fix the sucker without pulling the dash appart, there is just not enough space to get your hand in there, even with computer/kick pad/glove box removed, still no go, so if you want it shut (for colder air conditioning--recycled air) cut a peice of timbre as square as your finger and about 5 inches or a little longer, (longer is better then you can keep trimming it smaller to fit) and wedge the piece of timbre between the flap and inside the opening of the plastic box, WELLA! problem solved!
Or pull the whole dash apart and fit a new tiny rod that has broken!
But dont fear, its as common as getting slapped by your missus for perving on a chicky babe wearing G-STRINGS!