A cooling system for a vehicle which includes a coolant circuit for circulating coolant to cool a unit carried on the vehicle; a refrigerant circuit for circulating refrigerant for an air conditioner of the vehicle; and a heat exchanger connected to the coolant and refrigerant circuits, provided with a storage medium for storing cool of the refrigerant. The engaging surface between the operating shaft and the rotating body forms a curved surface having both arc element and noncircular element. A critical dimension is then measured for each of the regions in the photomask.