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Stepping motor for air-blending damper

Stepping motor for air-blending damper



The stepping motor has two windings. A voltage is applied to the windings in special order with short pulses. This causes the motor to move in short steps, hence its name. The direction of rotation can be changed. When the motor is stationary, current is applied continuously to both windings. A stepping motor requires no feedback to the ACC control module. By sending a definite number of pulses, the ACC control module always knows how much the damper moves. A condition for this is that the control module calibrates itself by rotating the damper to an end position so that the exact position of the damper is known. Calibration is carried out by means of an ISAT or by simultaneously pressing the AUTO and OFF buttons. Calibration must be carried out if the battery has been disconnected or discharged of if the ACC panel or stepping motors have been replaced. The air-blending damper is set by the ACC control module with the aid of the blended air temperature sensor so that a suitable air temperature will be obtained. The cabin temperature, selected temperature and outside temperature are decisive for the blended air temperature. If the air-blending damper is set at the position for maximum cold and this is still insufficient to maintain the selected temperature, recirculation will be selected. If the selected temperature is "HI" or "LO" the air blending damper will be set to the maximum heat or maximum cold position.