PURPOSE: To prevent a drop of a low pressure side pressure due to an insufficient refrigerant circulating amount at the time of a low load operation by connecting a control low pressure switch to a bypass solenoid valve of a bypass pipe for supplying a refrigerant by detouring a condensing pressure regulating valve by a wiring.

CONSTITUTION: The air-cooled type air conditioner comprises a control low pressure switch 23 provided at a pipe 22 for connecting an evaporator 4 of a low pressure side pipe to a compressor 1, a bypass solenoid valve 18 electrically connected to the switch 23. In the case of a low load operation, a solenoid valve 6 of a bypass route 10 is opened via a high pressure switch 11 to conduct a bypass operation. When an operation is continued for a long time so that circulating refrigerant is stored in an air cooled condenser 7 and a refrigerant pipe 8 with the result that an absolute amount of the refrigerant is insufficient and the pressure is lowered, the switch 23 is operated to open the valve 18. Then, part of the stored refrigerant is circulated via the condenser 7 and the pipe 8 to be supplemented to raise the low pressure side pressure to a normal refrigerating cycle. Accordingly, a drop of the low pressure side pressure due to insufficient refrigerant circulating amount at the time of the low load operation can be prevented.