PURPOSE: To adjust a blade in a given set position and to control air in a given direction by a method wherein when a blade position detected by a variable resistor coincides with data of an air direction, a rotation drive mechanism is stopped, and the position of a blade is always detected accurately.

CONSTITUTION: When a blade drive control circuit 7 receives air direction data of set switches 6a-6d, a signal from an A/D converter 8 is inputted so as to detect a present blade position. At the same time when a relay 5 is turned ON so that the blade is adjusted in a set position and an electric motor is run, a signal from an A/D converter 8 is always inputted to provide a state that a blade position is always detected. Since, when the blade position is adjusted to a set position, the resistance value of a variable resistor 4 is changed according to rotation of a cam, a signal from the A/D converter 8 produces a set position. The blade drive control circuit 7 detects the set position, the relay 5 is turned OFF to stop running of the electric motor, and the blade can be always stopped in a position. As a result, an air direction can always match the state of an air direction switch.