PURPOSE: To stabilize the heating operation and to save power consumption, in the heat pump type air conditioner having an electric heater for an auxiliary heat source, by automatically turning OFF a heater power supply and reducing the rotation of a fan for an outdoor heat exchanger at the time of the overload heating operation.

CONSTITUTION: When an overload operating state in heating occurs due to the increase in external air temperature, the contact point of a thermostat BT2 is opened based on the operation characteristics of the bimetal thermostat BT2, the excitation of a relay X is stopped, and contact points X1 and X2 are opened. Therefore, a current is not conducted through the electric heater H, and the total current of the air conditioner is suppressed to the maximum allowable current value or less. At the same time, the outdoor fan FM0 is switched to a low speed operation, the heat absorbing quantity in an evaporator is suppressed, and the increase in the input to a compressor CM is prevented. At this time, the temperature preset value of the bimetal thermostat BT2 is determined by the correlation of the compressor input, the heater capacity, and the rated current value. In this way, the power consumption is saved and the operation is stabilized.