GF83.40-P-2000RA Automatic Air Conditioning Control and Operating Unit, Function

GF83.40-P-2000RA Automatic Air Conditioning Control And Operating Unit, Function
- with CODE (494) USA version

Component Identification:

Function
The AAC pushbutton control unit (N22) makes it possible to make adjustments made by the driver and front passenger such as:

^ Temperature by setting the left (1) and right (2) temperature selector wheels
^ air quantity manually by setting the blower switch (5) or by pressing the Auto button
^ air quantity manually by setting the air distribution switches, left (3) and right (4) or by pressing the Auto button
^ Recirculated air mode by pressing the recirculated air pushbutton
^ Defrost function by pressing the defroster pushbutton
^ activating the residual engine heat utilization system with the ignition switched off by pressing the REST button
^ Switching off the cooling by pressing the AC OFF button
^ switching off the complete automatic air-conditioning system by pressing the ON/OFF button
^ switching on the heated rear window by pressing the button

The control unit integrated in the AAC pushbutton control unit (N22) looks after all system regulation and control functions such as:

^ comparing preselected/actual temperatures and controlling the air temperature at the air outlets
^ Automatic switchover from fresh air to recirculated air mode Actuating the refrigerant compressor
^ Actuating the refrigerant compressor
^ operating the engine/AC electric suction fan with integrated control
^ control of the air outlet openings

In maximum cooling operation, the MAX COOL symbol is illuminated on the temperature selectors.

The AAC pushbutton control unit (N22) continues to perform the following system actuations:
^ via the CAN data bus: refrigerant compressor; in-car temperature sensor; coolant circulation pump; engine and A/C electric suction fan with integrated control, and rear window heater
^ via the AAC data bus: blower regulator; 12 stepper motors for air distribution and temperature control

The following sensor signals are read in by the AAC pushbutton control unit (N22):
^ directly: in-car temperature sensor
^ analog 0 - 5 V: evaporator temperature sensor
^ via the CAN data bus: outside air temperature sensor; Vario roof position; refrigerant pressure and temperature sensor
^ via the overhead control panel control unit (N72): in-car temperature sensor
^ via the EIS control unit (N73): battery voltage; coolant temperature sensor; engine rpm; vehicle speed
^ via the instrument cluster (A1): circuit 58 d; detection of °C - °F

The AAC pushbutton control unit (N22) reads in the window, door and Vario roof settings in order to achieve better control quality when they are open.

The averaged value of the interior temperature with a window open, door open and vehicle speed = 0 km/h is also recorded for a maximum of 2 min. This ensures that the air conditioning system continues operating immediately with the set interior specified temperature.

The following system settings, which were activated before the engine was switched off, are stored by the AAC pushbutton control unit (N22) in the EIS control unit (N73).
^ AC OFF mode activated (yes/no)
^ Central automatic mode activated (yes/no)

When the engine is restarted, the status stored in the EIS (N73) control unit is reactivated.

The AAC pushbutton control unit (N22) has a diagnostic capability. Consequently, any faults which occur are stored in the fault memory which can be read with the help of the diagnosis system STAR DIAGNOSIS.
When the AAC pushbutton control unit is replaced (N22), control unit coding must be carried out using the diagnosis system STAR DIAGNOSIS.