PURPOSE: To enable to dispense with a clutch for stopping operation of a compressor for a car cooler, by connecting a discharge port and a suction port of the compressor by a by-pass pipe having a valve at a portion thereof.

CONSTITUTION: When a valve 6 is opened after stopping the operation of a car cooler, cooling medium discharged from a discharge port 2 of a compressor 1 is passed through a by-pass pipe 5 and the valve 6 and then drawn into a suction port 3 of the compressor 1. Therefore, pressure acted in a relief valve 4 becomes lower than a set value, so that the valve 4 is closed. In this state, cooling medium discharged from the compressor 1 is wholly carried from the discharge port 2 back to the suction port 3 via the by-pass pipe 5 and a valve 6, so that no power is consumed by the compressor 1 for compressing the cooling medium and it is made unnecessary to disconnect the engine power by means of a clutch. Thus, it is enabled to dispense with a clutch at the car cooler.