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Stepping motor, air distribution damper

Stepping motor, air distribution 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.

In AUTO position, floor and panel-floor are not used. If the required mixed-air temperature is high, the air distributor will move to the defroster-floor position. If the required mixed-air temperature is low, the air distributor will move closer still to the defrost position.

At required temperatures that are very low, the air distributor will move to the panel position.

As will be obvious, air distribution is a function of required mixed-air temperature. Desired air distribution can be selected manually on the ACC panel.

The position of the air distribution is indicated by a symbol on the ACC display panel.

Diagnosis

In case of an open circuit or short circuit, diagnostic trouble code BB2400 is generated, and 12 is shown instead of temperature at calibration.

If the motor binds, diagnostic trouble code B2406 is generated, and 13 is shown instead of temperature at calibration.

If the motor and damper lack mechanical connection, diagnostic trouble code B2405 is generated, and 14 is shown instead of temperature at calibration.