Have you had your HVAC controls stop working except for the defrost regardless of where the mixer dial was positioned? I did recently.
The fix is simple - you just need to know where to look.
Pop the hood and look at the intake manifold (on the driver side). You will soon discover that a hose has fallen off the intake manifold. I've circled where the problem is - the hose is hanging to the right of the nipple.
Slide the hose back on - you'll see how easy it slides on and will now know why it came off (too loose...). I plan to add a zip tie to mine shortly:
Locate this hose connection
Slip the hose back on
All done - took longer to read this than it will to fix it.
EDIT: If this doesn't fix your problem, then there are other issues at work. You might have something related to TSB # 242499 (HVAC changes to defrost under acceleration) or something else.