Underneath of the dash to the right of the steering column on the driver's side is a cam. It has an electric servo motor that moves it from floor to defrost. You can try reaching up there and helping it move and maybe you can lubricate it with some WD-40 and a straw. If you move the knob on the dashboard from Floor to defrost and hear a loud clicking sound you may get lucky and just may be stuck. If that does not help it maybe the electric servo motor is bad or the switch on a dashboard may be bad. The best I can remember there is a calibration procedure if this does not help I can post that.