A climate control system incorporated in a motor vehicle having a hydraulic pump directly driven by a vehicle engine to deliver a working oil under pressure to be supplied to either a hydraulic motor for driving a refrigerant compressor of an air-conditioning system or a heat conversion unit of the heating system via a hydraulic flow control valve for controlling the flow direction of the working oil. The air-conditioning system has an evaporator for cooling the air supplied to the vehicle compartment. In the heat conversion unit of the heating system, pressure energy of the working oil is converted to thermal energy thereof by which the engine cooling water is heated to thereby heat the air supplied to the vehicle compartment via a radiator unit made of a heater core.