PURPOSE: To prevent a breakage caused by freezing in a heating heat exchanger by a method wherein a fan motor is operated with forced air under a control of a timer circuit, a cooling heat exchanger temperature sensor and a microcomputer if a temperature of the cooling heat exchanger is decreased even if an indoor device is being stopped in its operation.

CONSTITUTION: If it is assumed that a stopping instruction is sent to a cooling outdoor device and a cooling heat exchanger 22 is kept at a temperature of 0°C irrespective of elapsing of a specified period of time, a microcomputer 5 judges that a cooling outdoor device 26 shows leakage in solenoid valves 30-a and 30-b in a freezing circuit or a control circuit at the cooling outdoor device 26 shows a runaway and a fan motor 9 is stopped, thereby the refrigerant is flowed and abnormally cooled. It further outputs signals to a fan motor circuit 6 and a display lamp control circuit 12. Irrespective of the fact that the outdoor device 21 is stopped, a fan motor 24 is operated with strong air, an abnormal cooling of the cooling heat exchanger is prevented through a heat exchanging operation with indoor air, thereby a breakage of the adjoining heating heat exchanger 23 caused by its freezing is prevented and at the same time an operation display lamp 13 is illuminated to display the abnormal state.