There is a door controled by the climated control on the passenger side . I bet its stuck open. I had the same problem, except door was closed. I was freezing to death in the winter . There is some type of electronic control box over there, I had to replace mine with one from the junker. I was a a while a go so IM a little fuzzy on it. A FSM would be helpful.
Remove glove box liner. Look upwards towards the defrost ducting. Locate the metal threaded rod that should be connected to a white plastic retainer. That retainer comes out of the climate programmer. Gently disconnect the rod by lifting up to unsnap it. Now with the car running and at normal temperature verify that this rod moves to close the blend door then fully open to open the blend door. Assuming it moves, pull the threaded rod to that retainer and snap the rod back on at the 90 degree setting ( you will hear the blend door fully open). Now, assuming everything is working as designed, you should see the rod disappear towards the dash at 60 degrees, then pivot back toward you at 90 degrees. I think the rod is misadjusted, leaving the blend door not fully shut at 60 degrees. Also while you're looking at the rod, notice the ribbed plastic hose coming from the programmer up into the dash top. Make sure that hose is NOT kinked and is fully on the nipple on the programmer. That hose sucks in interior air to tell the programmer where to move the blend door. If kinked or off, the programmer delays or never gets that signal to adjust the temperature to what you've set on the display.
And....... this should have been a new thread, not tacked onto a 3 yr old topic.