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Stepping motor, air distribution flap

Stepping motor, air distribution flap





The stepping motor has two windings. The windings are energized 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 energized 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 is performed by pressing the rear window heater button for more than 5 seconds. Calibration must be performed if the stepping motor is replaced or its position is changed.

If the battery has been disconnected/discharged or the MCC unit removed or replaced, calibration will be performed automatically when the ignition is turned on.

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 operated by a stepping motor fitted to the passenger side of the climate housing .

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 outlets.

The stepping motor for the air distribution flap is supplied with current from the MCC unit pins 27 and 8 (winding 1) and pins 28 and 9 (winding 2).

Diagnostics

In the event of an open circuit or short circuit in the circuits to any of the stepping motors, diagnostic trouble code 7 is set. If the motor jams, diagnostic trouble code 6 is set. Diagnostic trouble code 3 is set if there is no mechanical contact with the flap. A stored code is flashed 6 times in succession by the LED for the electrically heated rear window if the button is depressed while turning on the ignition, and for a further 2 seconds after that.

Only one fault can be stored at any one time. Diagnostic trouble codes are deleted by calibration after correcting the malfunction.