An air conditioning system that includes a casing that has a flow channel connected to an inside of a vehicle to supply or discharge air. A motor is mounted on one side of the casing to generate a normal direction torque and a reverse direction torque and a first fan is disposed on one side of the flow channel to be connected to an output shaft of the motor and to be rotated. A second fan is disposed on one side of the first fan to be fixedly mounted in the shaft and to be rotated. Additionally, a variable connecting unit that connects the first fan to the shaft of the motor is rotated when the motor is rotated in a normal direction and has a torque of the shaft of the motor not to be transmitted to the first fan when the motor is rotated in a reverse direction.