PURPOSE: To expand a cooling operation available region under a low temperature condition and prevent an air blowing temperature from being decreased by a method wherein a temperature of an indoor evaporator or an air blowing temperature is detected, an outdoor air blower is varied at its fan speed in response to a value of a detected temperature or its on-off operation is carried out.

CONSTITUTION: An indoor pipe temperature thermistor 2a of a main body 1 inputs a temperature variation into an indoor micro-computer 3 as a divided voltage with a resistor Ra. A pipe temperature data is compared with a predetermined temperature and studied by a comparator 4, a signal of either stopping or operation is instructed to an outdoor air blower 6 of a main body of an outdoor device in response to a result of comparison, an outdoor fan selector switch 7 is operated to control an outdoor air blower 6. If a pipe temperature T is lower than a set temperature Ta, the outdoor air blower 6 is stopped and in turn if the pipe temperature T is higher than a set temperature Tb, the outdoor air blower 6 is operated. During a cooling operation under a low indoor atmospheric temperature, a freezing of the indoor heat exchanger is prevented, a more cooling operation range is expanded and at the same time a reduction of an air blowing temperature is prevented.