96 - Climate Control stuck on Defrost/Floor bi-level

I have a 96 2-door SE. I went to use the AC today and noticed that the dashboard vents will not work. In fact, the blower will only blow air (doesn't matter if its AC or heat) out through the dash defroster vent and the floor vents. It doesn't matter what I have the knob set to either, for some odd reason it is perm. stuck on the defrost/floor setting, which is the last thing I had the knob turned to last week when everything was still working right. The knob does turn the AC light on and off like it should when you switch it from total defrost to defrost/floor or over to the far left which is Max AC. Has anyone else ever had this problem or have any suggestions? Any input you may have will be much appreciated....

Usually this is a default mode for the Hvac system. If you have vaccum operated diaphrams it would mean more than likely you lost vaccum to the diaphrams and they cannot move the doors to change .

Does the air on the floor is cool(aka does the ac compressor works) because it true you lost vacum (if your diaphragms are a vacum operated) that is why they do not change settings even when you turn the setting knob. The AC circuit could be at fault and not engaging the compressor either.