Why won't the air blow out of the feet or face or defrost according to the contr on 2002 Pontiac Sunfire

With the AC running, when I put the controls to feet only, the air blows out the feet, but when I set it to blow on the face only or defrost, it blows on the feet. What is the problem? I do not hear a vacuum noise when changing the setting.

check your blend door actuator