Control and operating unit comfort automatic air conditioning, task - GF83.40-P-2181-01PP

Shown on comfort AAC control and operating unit (N22/7) as of 1.6.02 

Task 

The comfort AAC control and operating module (N22/7) controls and regulates all air conditioning functions for the vehicle interior.

• harmonizing the temperatures preselected and actually present and controlling the air outlet temperature at the air vents.
• Automatic switcher from fresh air to recirculated air mode
• Electrical control of refrigerant compressor
• Operating the engine/AC electric suction fan with integrated control

The following additional functions are also regulated by the comfort AAC control and operating unit (N22/7) and the required information forwarded to the processing control units via the Controller Area Network bus class B (interior) (CAN-B).

• Heated rear window
• Stationary heater (on vehicles with code (228) stationary heater)

The comfort AAC control and operating module (N22/7) performs the following system actuations: 

• via the CAN-B: refrigerant compressor; coolant circulation pump; engine and AC electric suction fan with integrated control; heated rear window
• via the A/C bus: blower regulator; 10 actuator motors for the air distribution

The following sensor signals are transmitted by the comfort AAC control and operating unit (N22/7) via the CAN-B: 

• Sun sensor values: the overhead control panel control unit reads in these values for the automatic driving light actuation in order to achieve a better information flow for this system.
• Dew point temperature: the left front door control unit and the right front door control unit read in this value in order to implement a demand-based heating of the outside mirrors.

The following sensor signals are received by the convenience AAC push-button control unit (N22/7): 

• installed sensor: in-car temperature sensor (N22/7b1)
• direct: evaporator temperature sensor
• via the CAN-B: outside temperature display temperature sensor; refrigerant pressure and temperature sensor
• via the electronic ignition switch control unit: battery voltage; coolant temperature sensor; engine speed
• via the instrument cluster: vehicle speed
• via the A/C bus: C-AAC sun sensor (4 in total); C-AAC multifunction sensor

The comfort AAC control and operating unit (N22/7) reads in the window and door positions as well as the position of the tilting/sliding roof (with code (414) Electric glass titling/sliding roof) in order to achieve an improved control quality in the open position.

The averaged value of the interior temperature with a window open, door open and ground 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 convenience AAC push-button control unit (N22/7) in the EIS control unit. 

• AC OFF mode activated (yes/no)
• Activated charcoal filter activated (yes/no)
• Automatic mode with automatic blower control and left/right air distribution activated (yes/no)
• At manual setting: Set blower speed and air distribution
• Set temperatures specified value

When the engine is restarted, the status stored in the EIS control unit is reactivated. The convenience AAC push-button control unit (N22/7) has a diagnostic capability. As a result, any faults which occur are stored in the fault memory which can be read out with the aid of the STAR DIAGNOSIS system.

When the comfort AAC control and operating unit (N22/7) is replaced, a variant coding has to be carried out with the aid of STAR DIAGNOSIS.

Temperature buttons warm (1 and 2) and cold (3 and 4) 

Pressing the temperature buttons warm (1 or 2) or cold (3 or 4) on the comfort AAC control and operating unit (N22/7) sets the desired interior temperature separately for left and right.

The comfort AAC control and operating unit (N22/7) compares the desired temperature with the temperature in the vehicle interior, which is measured by the in-car temperature sensor (up to 31.5.02) in the overhead control panel control unit and additionally by the in-car temperature sensor (N22/7b1) on the comfort AAC control and operating unit (N22/7).

By comparing the actual values and the specified values the comfort AAC control and operating module (N22/7) determines the correct position of the blend air flaps and actuates these separately for the left and right. The selected temperature is reached and maintained as quickly as possible, if warming or cooling of the interior is necessary.

Defroster button (5) 

Pressing the defroster button (5) initiates the defrost function.

The defroster function works according to the following new logic:

• heating power is controlled by the outside temperature.
• the entire air flow is directed at the windshield and the front side windows, and the defroster nozzles are opened.
• the blown-in air is dehumidified depending on the humidity in reheat mode
• blend air flaps controlled
• footwell vents closed
• blower power at 80 %, can be manually controlled

Blower button (6) 

The blower button (6) switches the control voltage for the blower regulator in 7 stages (indicated in the display (11) by 7 wedge display segments), depending on the position via the comfort AAC control and operating unit (N22/7). This facilitates control of the blower speed from 0 to 100 %.

AC OFF button (7) 

When the AC OFF button (7) on the comfort AAC control and operating unit (N22/7) is pressed (the LED comes on), the refrigerant compressor is shut off and thus the cooling mode is switched off. The air is no longer cooled and dried.

In vehicles with diesel engines the heater booster control unit is also shut off. All other functions are retained. The pollutant-controlled recirculated air function is not available in AC OFF mode.

In order to shut off the refrigerant compressor, the comfort AAC control and operating unit (N22/7) transmits the shutoff request and the specified value = 0 % to the front SAM control unit with fuse and relay unit via CAN-B. At the same time, the refrigerant compressor torque is set to "0" and transferred to the engine electronics and the electronic transmission control via the EIS control unit. The front SAM control unit with fuse and relay module sends the canceled load increase signal to the engine electronics via the EIS control unit and switches the refrigerant compressor off after a defined time delay.

The AC OFF button (7) was installed in the comfort AAC control and operating unit (N22/7) as an EC button in vehicles up to 31.5.02. The EC button has the same tasks and functions as the AC OFF button (7), which was installed as of 1.6.02.

Rest button 

When the REST button (which is combined with the AC OFF button (7)) is pressed, the residual engine heat utilization is switched on.

When the engine is switched off, the residual heat heats the vehicle depending on the temperature setting on the comfort AAC control and operating module (N22/7) and the ambient temperature in the vehicle interior.

The vehicle can be heated for approx. 30 minutes with the engine switched off. The function is only available when the ignition is switched off or the transmitter key in the EIS control unit is in position 1. The residual engine heat utilization system is switched off automatically in the event of undervoltage.

The flaps for the air distribution and the air volume are regulated automatically.

The residual heat function is switched off,

• if the transmitter key in the EIS control unit is turned to position 2,
• after approx. 30 min. or
• if the battery voltage drops below 11 V.

Left Auto button (8) and right Auto button (9) 

By pressing the left Auto button (8) or right Auto button (9), which are combined with the left and right air distribution switches, the automatic mode for the left and right sides can be activated separately. The system switches back to manual mode by subsequently rotating the air distribution switch.

In automatic mode, in addition to temperature control the blower output and air distribution are controlled automatically.

The blower speed is continuously controlled depending on the temperature difference between the specified and actual values. For electronic control of the system humidity is also used in addition to interior temperature.

In automatic mode, cooled air may also flow out of the defroster vents.

The prerequisites for this are as follows

• an adjusted automatic air distribution
• dry weather (recognition of humidity by the C-AAC multifunction sensor) in order to keep the windows free from misting up.

Air distribution switch on left and right 

The air distribution can be set manually or automatically:

• Manually (left Auto button (8) or right Auto button (9) not engaged)
  • Turning the air distribution switch on left and right
  • Display by white printed notch
• Automatically (left Auto button (8) or right Auto button (9) engaged)
  • Display through "AUTO" symbol in display (11)

Turning the air distribution switch on left and right on the comfort AAC control and operating unit (N22/7) actuates the various actuator motors for air distribution via the A/C bus.

Apart from the 4 listed basic settings, a further 8 intermediate settings can be selected.

Activated charcoal filter button (10) 

Pressing the activated charcoal filter button (10) on the comfort AAC control and operating unit (N22/7) switches to operation with the activated charcoal filter; this conducts incoming fresh air, after flowing through the dust filter, through the activated charcoal filter. Pressing the activated charcoal filter button (10) actuates the activated charcoal filter flap adjustment motor, which closes the activated charcoal filter flap in the AC housing and thus conducts the air through the activated charcoal filter.

As a result, the pollutant content in the fresh air is reduced and the odor emission decreased. With an increased CO and NOx content in the outside air, recirculated air mode is selected automatically with the aid of the C-AAC multifunction sensor. Air recirculation mode which is regulated as a function of pollutants is not possible in the AC OFF mode and with outside temperatures less than 5 °C.

Display (11) 

The display (11) serves to inform the driver about any adjustments to the ventilation and comfort automatic air conditioning. The information is provided in form of the words, symbols and digits.

Dependent on the setting created via the multifunction steering wheel, the temperature is either displayed in °C or in °F in the display (11). Other messages are presented by means of the corresponding symbols.

The display employs a negative technology design, in other words light digits against a dark background.

Air recirculation switch (N22/7s2) 

A short press <1,5 s of the air recirculation switch (N22/7s2) actuates the fresh air/air recirculation flap actuator motor, which operates the fresh air/air recirculation flap and thus closes the fresh air opening and opens the recirculation duct in order to enable the air to be supplied from the vehicle interior. The LED in the air recirculation switch (N22/7s2) is illuminated in air recirculation mode.

Recirculation air convenience closing function 

If the air recirculation switch (N22/7s2) is pressed for longer than 1.5 s, all open windows and the tilting/sliding roof (with code (414) Power glass tilting/sliding roof) are closed in automatic mode (windows and tilting/sliding roof have to be normalized) in addition to the recirculated air function. The LED in the air recirculation switch (N22/7s2) is illuminated in air recirculation mode. Sliding/tilting roof and power windows are operated one after the other in order to avoid current peaks.

If it is operated once again > 1.5 s, the windows and the tilting/sliding roof are moved back into the previously stored positions and the fresh air/air recirculation flap moves into the fresh air position (function LED off).

The convenience closing function can only be started if the LED in the air recirculation switch (N22/7s2) or the LED in the activated charcoal filter button (10) is not illuminated.

Any window which has been opened manually during this recirculation air phase, remains in this position when the recirculation air function is canceled, all other windows move into the stored position. The positions of the tilting/sliding roof and of the side windows which existed prior to the commencement of the closing operation, are stored by the overhead control panel control unit or by the door control units. The windows and the tilting/sliding roof, which were closed by means of the convenience closing function, remain closed if the air recirculation switch (N22/7s2) is pressed for <1.5 seconds. In this case only the fresh air/air recirculation flap is moved into the fresh air position. The stored positions are canceled when the ignition is switched off.