An automotive air conditioning system includes: an air conditioning duct having an outlet; an evaporator; a heater core; an air mix door that divides air passing through the air conditioning duct into to pass through the heater core and to bypass the heater core; an outlet air temperature sensor; a control unit; a primary bypass passageway defined by the air mix door; a secondary bypass passageway different from the primary bypass passageway; and a cold air controlling door that controls an air flow rate in the secondary bypass passageway. The control unit sets an opening for the air mix door to obtain air conditioned to the target outlet air temperature when the cold air controlling door is opened to an initial opening and controls the opening to cause a temperature detected by the outlet air temperature sensor to approach a target outlet air temperature.