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Stepping motor, air distribution flap

Stepping motor, air distribution flap


The stepping motor has two windings. The windings are energised in a special order with short pulses. This makes the motor move in short steps, which is how it got its name. The direction of rotation can be changed. When the motor is stationary, both the windings are energised continuously to lock the motor. The stepping motor does not require a feed-back coupling to the control module (position sensor). By sending a known number of pulses, the control module always knows how far the flap has moved. This is possible on condition that the control module has calibrated itself by turning the flap to its respective end positions so that it knows the position of the flap.

Calibration takes place by pressing the AUTO and REC buttons. A sound and the message, ACC:CALIBR. STARTED are indicated in the main instrument unit, confirming the calibration. Calibration must take place if the battery is disconnected/discharged, if the ACC unit or stepping motor is replaced, or their positions are changed.

The climate system has two air distribution flaps, one twin-flap for the driver's zone and the front seat passenger, and one for the rear seat passengers that is linked to the front flap. The two flaps are manoeuvred by a stepping motor fitted to the passenger side of the heating and ventilation unit. Consequently, the air distribution is common for the passenger and the driver zones. The air is distributed to the defroster, floor/rear door windows or the dashboard/rear centre vents.

The stepping motor for the air distribution flap is supplied with current from the ACC unit's K1 pins 38 and 36 (winding 1) and K1 pins 37 and 35 (winding 2).

The air distribution is controlled depending on the requested mixed air temperature for the driver's zone.

Defrost is selected first after cold starting, see Starting from cold in auto .

Required air distribution can also be selected manually on the panel.

In the OFF position the flap stops in the last selected position.

When the ignition is switched off the air distribution flap will first stop in the latest selected position.

After 8 minutes and when the outside temperature is under 18°C the air distribution flap moves to park position floor (50%). If the outside temperature rises above 18°C the air distribution flap moves to ventilation (0%).


Diagnostics

In the event of open circuit or short circuit diagnostic trouble code B2400 is generated.

The diagnostics tool shows 100% in defrost position and 0% in panel position.