PURPOSE: To prevent a magnet clutch from seizing by carrying out normal variable capacity control during inner air circulation and minor quantity control during outer air introduction, and by eliminating abnormal rise of the discharge pressure of compressor.

CONSTITUTION: The body of a control device includes a refrigerator circuit, in which a variable capacity compressor 1, condenser 2, receiver dryer 3, automatic expansion valve 4 and evaporation 5 are connected with one another. These components 4-6 are arranged in a duct 7 to constitute a unit 8. The changeover position of an intake door 9 installed rotatably at the inlet to the duct 7 is sensed by a limit switch 12. On the basis of this sensed changeover position, an electromagnetic actuator 1a driving the compressor 1 is controlled by a control circuit 13. That is, normal variable capacity control is conducted during inner air circulation, while minor capacity control is carried out during outer air introduction.