A vehicular air conditioning system may include a cam plate rotatably coupled to an air conditioning case via a cam shaft, wherein a portion of the cam plate may be connected to a regulating knob via a cable for selecting an air conditioning mode and wherein a portion of the cam plate may be integrally formed with a cam pivot projecting toward the air conditioning case, and an arm rotatably coupled to the air conditioning case via a door shaft and formed with a guide slot into which the cam pivot may be inserted, wherein the arm may be configured to rotate about the door shaft while the cam pivot pushes a portion of the guide slot as the cam plate rotates.