when I turn knob to change where the air comes nothing moves? on 2001 Hyundai Elantra

When I change the know for the heat/air to move wheren the air flow comes out (feet, vents, deforst) nothing will change, it stays in the same location.

Asked by for the 2001 Hyundai Elantra
Likely a controller or linkage problem or blend door prob. Try this site for some help. Hyundai tech service Same info factory trained techs use.