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Stepping motor, air-mixing damper

Stepping motor, air-mixing damper





The stepping motor has two windings. A voltage is applied to the windings in special sequence in short pulses. This causes the motor to move in short steps, hence its name. The rotational direction can be changed. When the stepping motor is stationary, both windings are continuously energised in order to lock the motor. The stepping motor does not need to be reconnected to the control module (position sensor). By sending a definite number of pulses, the control module always knows how far the damper has moved. The condition is that the control module has calibrated itself by turning the damper to the respective end positions so that the control module knows the position of the damper.

Calibration is performed by simultaneously pressing the AUTO and OFF buttons. Calibration must be performed if the battery has been disconnected/removed, if the ACC unit or the stepping motor has been replaced or its position has been changed.

The air-mixing damper is set by the ACC control module using the mixed-air temperature sensor to achieve a suitable mixed-air temperature.

The cabin temperature, selected temperature and outside temperature are decisive for the blended-air temperature. If the air-blending flap is in the max. cold position and this is still not enough to maintain the selected temperature, recirculation will be selected.

If the selected temperature is “HI” or “LO”, the air-mixing damper will be set in the max heat respective max cold position.

Diagnosis

In case of an open circuit or short circuit, diagnostic trouble code B2492 is generated, and 06 is shown instead of temperature at calibration.

If the engine binds, diagnostic trouble code B2496 is generated, and 07 is shown instead of temperature at calibration.

If the motor and damper lack mechanical connection, diagnostic trouble code B2495 is generated, and 08 is shown instead of temperature at calibration.