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Regulation of Automatic air conditioning, function - GF83.40-P-2004LE

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MODEL 216.3, 221.0 /1 (except, 221.095 /195) as of model year 2009 /YoM 08 

Function requirements, general 

IMPORTANT Status of circuit 15 is provided by EZS control unit (N73) via interior CAN (CAN B). The status of circuit 61 is provided by the CDI control unit (N3/9) (model 221 with diesel engine) or by the ME-SFI [ME] control unit (N3/10) (with gasoline engine) via chassis CAN (CAN E) and forwarded by the central gateway control unit (N93) via interior CAN to the AAC [KLA] control unit (N22/1).

Automatic air conditioning regulation, general 

The electronic regulation of the temperature and the air distribution in the interior compartment takes place depending on the settings selected at the upper control panel control unit (N72/1), at the front central operating unit (A40/9) or at the rear air conditioning control unit (N22/4) (with code (582) Rear air conditioning) and the variables measured by various sensors (e.g. outside temperature, interior temperature, coolant temperature).

The determination of these variables will be described following the description of the settings that are relevant for regulation.

The regulation and control are performed by the AAC [KLA] control unit. This is networked with the vehicle electronics system via the interior CAN, the climate control LIN (LIN B8), the A/C bus (KB) and direct lines.

This in turn makes it possible to incorporate relevant parameters in order to improve the regulation quality of the automatic air conditioning and to lower power consumption.

The automatic air conditioning regulation comprises the following subfunctions:

Function sequence for adjustments that are relevant for regulation 

The function sequence for adjustments that are relevant for regulation comprises the following subfunctions:

Additional function requirements, automatic regulation 

Function sequence for automatic regulation 

The temperature, the air distribution and the air volume are regulated depending on the temperature preselection at the upper control panel control unit, at the front central operating unit or at the rear air conditioning control unit (model 221) and the prevailing general conditions. The air distribution and air volume are set automatically.

The following variables are taken into account by the AAC [KLA] control unit:

Additional function requirements, manual regulation 

Function sequence for manual regulation 

The temperature, the air distribution and the air volume are regulated depending on the settings made at the upper control panel control unit, at the front central operating unit or at the rear air conditioning control unit (model 221 with code (582) Rear air conditioning) and the prevailing general conditions. In this case, some of the same variables as for the automatic regulation are taken into account by the AAC [KLA] control unit.

Additional function requirements, defroster function 

Function sequence of defroster function 

Pressing the defrost/heated windshield button on the upper control panel control unit closes all air flaps except for the defroster flaps and the fresh air flap. These are fully opened. The defroster and side air vents are adjusted such that the maximum air flow is directed to the windshield and the front side windows. When the engine coolant is cold, the air volume is reduced. The air conditioner water valve (Y19/2) is opened, and the heater circulation pump (M13) and if necessary the PTC heater booster (R22/3) (with diesel engine) are actuated.

The blower motor (A32m1) is actuated by the AAC [KLA] control unit via the blower regulator (A32n1) to ensure the best possible defrost mode dependent on the temperature of the air flowing out. The refrigerant compressor is activated in order to ensure that the air flowing out is dried. The air is dried (cooled) and then heated up to the maximum temperature.

IMPORTANT If the "Defrost" function is active, the entries for air distribution, recirculated air and A/C are locked.

IMPORTANT With code (582) Rear air conditioning (model 221), the symbols "OFF" and "Rear remote control" appear in the display of the rear air conditioning control unit. The rear air conditioner is switched off. The buttons of the rear air conditioning control unit are locked.

Additional function requirements for maximum cooling output (with code (494) USA version) 

Function sequence for maximum cooling output (with code (494) USA version) 

Setting the maximum cooling output at the upper control panel control unit or at the front central operating unit raises the basic ventilation level to P = 100 %. In the COMAND display (A40/8) (without code (867) SPLITVIEW) or in the SPLITVIEW display (A40/10) (with code (867) SPLITVIEW), the words "MAX COOL" are shown.

IMPORTANT With code (582) Rear air conditioning and "MONO" mode active, the rear air conditioning control unit receives the message "MAX COOL" from the AAC [KLA] control unit. This setting data is taken over by the rear air conditioning control unit. The words "MAX COOL" also appear in the rear display.

Function sequence, determining variables 

The function sequence for determining variables comprises the following subfunctions:

D Function sequence for determining the outside temperature 

D Function sequence for determining the interior temperature 

D Function sequence for determining the coolant temperature 

D Function sequence for determining the temperature at the air outlets in the vehicle 

D Function sequence for determining the vehicle speed 

D Function sequence for determining the solar radiation on the vehicle 

D Function sequence for determining the temperature at the evaporator and at the rear air conditioning evaporator (model 221 with code (582) Rear air conditioning) 

D Function sequence for determining the temperature downstream of the rear air conditioning heater core (model 221 with code (582) Rear air conditioning) 

D Function sequence, determining the settings at the air outlets 

D Function sequence for determining the refrigerant pressure 

D Function sequence for determining the engine speed 

D Function sequence, determining the pollutant concentration of the outside air 

D Function sequence, determining the dew point temperature 

D Function sequence for determining the door status 

D Function sequence for determining side window position 

D Function sequence for determining the SHD position (with code (414) Power glass tilting/sliding roof) or the panoramic sliding sunroof position (model 221.1 with code (413) Panoramic glass sunroof with top sliding sunroof) 

D Function sequence for determining the VCS [SBS] status (without code (526) COMAND with single DVD drive (without navigation)) 

D Function sequence, determining the settings at the upper control panel control unit and at the front central operating unit 

D Function sequence for determining the settings at the rear air conditioning control unit (model 221 with code (582) Rear air conditioning) 

Function sequence, determining the outside temperature 

The outside temperature is recorded by the outside temperature indicator temperature sensor (B14). The front SAM control unit with fuse and relay module (N10/1) reads in the value of the outside temperature directly and transmits it via the interior CAN to the AAC [KLA] control unit.

Function sequence for determining the interior temperature 

The interior temperature is measured by the in-car temperature sensor (B10/4). The AAC [KLA] control unit reads in the value of the interior temperature directly, evaluates it and regulates the interior temperature largely independently of the flow conditions in the vehicle interior.

Function sequence for determining the coolant temperature 

The value of the coolant temperature is used to control the blend air flaps, to actuate the heater circulation pump and for many other internal computations.

The temperature of the engine coolant is measured by the coolant temperature sensor (B11/4). The CDI control unit or the ME-SFI [ME] control unit reads in the recorded value of the coolant temperature sensor directly and provides it via chassis CAN. The central gateway control unit forwards this via interior CAN to the AAC [KLA] control unit.

Function sequence for determining the temperature at the air outlets in the vehicle 

The temperature at the air outlets is measured by the left side air vent temperature sensor (B10/31), by the right side air vent temperature sensor (B10/32), by the left footwell temperature sensor (B10/35) and by the right footwell temperature sensor (B10/36).

The AAC [KLA] control unit reads in the values of the temperature sensors directly and regulates the outlet air temperatures of the particular air outlets.

Function sequence for determining the vehicle speed 

The current vehicle speed is provided by the instrument cluster (A1) via central CAN (CAN F). The central gateway control unit transmits sends this via interior CAN to the AAC [KLA] control unit. The vehicle speed is used for the internal calculation of the outside temperature, e.g. during operation while standing.

Function sequence for determining the solar radiation on the vehicle 

The intensity and the angle of incidence of the solar radiation on the vehicle are recorded by the AAC [KLA] sun sensor (4 in total) (B32/2). The AAC [KLA] control unit reads in the data from the AAC [KLA] sun sensor (4 in total) via the A/C bus and adapts the interior temperature and the blower speed accordingly. In the event of one-sided solar radiation, an adequate temperature difference is set between the left and the right regulated specified temperatures.

Function sequence, determining the temperature at the evaporator and at the rear air conditioning evaporator (with code (582) Rear air conditioning) 

To prevent the evaporator from icing up, the local temperature is constantly recorded. The temperature at the evaporator is recorded by the evaporator temperature sensor (B10/6). The temperature at the rear air conditioning evaporator (model 221 with code (582) Rear air conditioning) is recorded by the rear air conditioning evaporator temperature sensor (B10/11).

The values for the evaporator temperature sensor are read in directly by the AAC [KLA] control unit.

If the evaporator temperature drops to T = 2 °C, the refrigerant compressor or the rear air conditioning refrigerant shutoff valve (Y67) (model 221 with code (582) Rear air conditioning) is shut off.

Function sequence for determining the temperature downstream of the rear air conditioning heater core (model 221 with code (582) Rear air conditioning) 

The temperature of the air flow downstream of the rear air conditioning heater heat exchanger is measured by the left rear air conditioning heat exchanger temperature sensor (B10/9) and by the right rear air conditioning heat exchanger temperature sensor (B10/10).

The AAC [KLA] control unit reads in the values of the rear air conditioning heat exchanger temperature sensor directly, calculates the opening period of the left duovalve (A31/1y1) and the right duovalve (A31/1y2) in the rear heating system feed unit (A31/1), which are then actuated accordingly.

Function sequence, determining the settings at the air outlets 

The settings at the air outlets are recorded by the following components:

The recorded values of the potentiometers are read in directly by the AAC [KLA] control unit.

Function sequence, determining the refrigerant pressure 

The refrigerant pressure is registered by the refrigerant pressure sensor (B12). The refrigerant pressure sensor is read in directly by the AAC [KLA] control unit.

If the pressure is too high or too low, the AAC [KLA] control unit shuts off the refrigerant compressor.

Function sequence for determining the engine speed 

The engine speed is used, among other things, to regulate the refrigerant compressor and is provided by the CDI control unit or by the ME-SFI [ME] control unit via chassis CAN and forwarded by the central gateway control unit via interior CAN to the AAC [KLA] control unit.

Function sequence, determining the pollutant concentration of the outside air 

The KLA [AAC] multifunction sensor (B31/1) records the pollutant concentration of harmful gases carbon monoxide (CO) and nitrogen oxide (NOX ) in the outside air.

The values of the AAC [KLA] multifunction sensor are read in by the AAC [KLA] control unit via the A/C bus. The AAC [KLA] control unit controls the automatic recirculation according to the values read in.

Function sequence, determining the dew point temperature 

The AAC [KLA] multifunction sensor uses the ambient temperature and air humidity to calculate the dew point and makes this available to the AAC [KLA] control unit via the A/C bus.

On reaching the dew point, the windows and the glass of the outside mirror begin to get fogged. To prevent this, the AAC [KLA] control unit activates the automatic climate control and the heated outside mirror.

In addition, the evaporator temperature and the opening angle of the defroster flaps are regulated depending on the dew point temperature.

Function sequence for determining the temperature and humidity at the windshield (as of 1.9.10 with code (B03) ECO start/stop function) 

The vehicle interior humidity/temperature sensor (B82) measures the relative humidity and temperature directly at the inside of the windshield and uses this to determine the dew point temperature. The AAC [KLA] control unit reads in the values of the vehicle interior humidity/temperature sensor via A/C bus. The AAC [KLA] control unit sends the "Circuit 61 ON" request to the CDI control unit or ME-SFI [ME] control unit so that the engine is started and the refrigerant compressor runs, thereby preventing the windshield from becoming fogged. The exact measurement process enables activation of the measures as late as possible, but as early as necessary.

Function sequence for determining the door status 

When a vehicle door is open, the AAC [KLA] control unit calculates the current inside temperature after a short delay in order to prevent unnecessary readjustment in the event of large temperature differences between the inside and outside air. The status of the particular vehicle doors is made available via interior CAN by the AAC [KLA] control unit:

Function sequence for determining side window position 

When the side windows are open, the AAC [KLA] control unit calculates the current inside temperature after a short delay in order to prevent unnecessary readjustment in the event of large temperature differences between the inside and outside air.

The positions of the side windows are made available to the AAC [KLA] control unit via interior CAN:

Function sequence for determining the SHD position (with code (414) Power glass tilting/sliding roof) or the panoramic sliding sunroof position (model 221.1 with code (413) Panoramic glass sunroof with top sliding sunroof) 

When the tilting/sliding roof or the panoramic sliding sunroof is open, the AAC [KLA] control unit calculates the current inside temperature after a short delay in order to prevent unnecessary readjustment in the event of large temperature differences between the inside and outside air.

The position of the tilting/sliding roof is made available via interior CAN by the overhead control panel control unit (N70) and read in by the AAC [KLA] control unit.

The position of the panoramic sliding sunroof (model 221.1) is provided by the panoramic sliding sunroof control module (A98) via interior CAN and read in by the AAC [KLA] control unit.

Function sequence for determining the VCS [SBS] status (without code (526) COMAND with single DVD drive (without navigation)) 

With active voice control system, the blower output of the blower regulator is limited. The COMAND controller unit (A40/3) sends the status of the voice control system via central CAN to the central gateway control unit and from there via interior CAN to the AAC [KLA] control unit.

Function sequence, determining the settings at the upper control panel control unit and at the front central operating unit 

The automatic air conditioning functions can be set by the driver and the front passenger via the upper control panel control unit and the front central operating unit.

The settings at the upper control panel control unit are transmitted to the AAC [KLA] control unit via interior CAN.

The settings at the front central operating unit are forwarded to the COMAND controller unit via telematics CAN (CAN A), transferred via central CAN to the central gateway control unit and from there via the interior CAN to the AAC [KLA] control unit.

Function sequence for determining the settings at the rear air conditioning control unit (with code (582) Rear air conditioning) 

The rear area automatic air conditioning functions can be adjusted by the rear occupants via the rear air conditioning control unit.

The rear AC control unit is a pure operating unit.

The settings at the rear air conditioning control unit are sent to the COMAND controller unit via telematics CAN, to the central gateway control unit via central CAN and from there via interior CAN to the AAC [KLA] control unit. The AAC [KLA] control unit performs all the actuations of the automatic air conditioning functions in the rear.

Function sequence for AC component actuation 

The AC component actuation function sequence comprises the following subfunctions:

D Function sequence, actuation of the refrigerant compressor 

D Function sequence for actuation of the refrigerant compressor magnetic clutch (A9y1) (with engine 642.8 and engine 651 as of 1.6.11) 

D Function sequence, actuation of the PTC heater booster (for diesel engine) 

D Function sequence for actuation of blower motor and rear blower motor (M2/1) (with code (582) Rear air conditioning) 

D Function sequence for actuation of the air ducting flaps 

D Function sequence for actuation of engine and air conditioning electric suction fan with integrated control (M4/7) 

Function sequence, actuation of the refrigerant compressor 

The refrigerant compressor is responsible for induction and compression of the refrigerant.

The refrigerant compressor output is regulated continuously up to P = 100% by the AAC [KLA] control unit via the compressor control valve.

The AAC [KLA] control unit transmits the refrigerant compressor switch-on request directly to the compressor control valve.

Function sequence for actuation of the refrigerant compressor magnetic clutch (with engine 642.8 and engine 651 as of 1.6.11) 

To prevent the refrigerant compressor from turning with the air conditioning switched off, the belt pulley is disconnected from the drive shaft of the refrigerant compressor by means of the refrigerant compressor magnetic clutch. Fuel is thereby saved.

The AAC [KLA] control unit sends the request for actuation of the refrigerant compressor magnetic clutch via interior CAN to the central gateway control unit.

The central gateway control unit sends the request via chassis CAN to the CDI control unit. This actuates the fuel pump relay (N10/2kS). The fuel pump relay controls the power supply of the refrigerant compressor magnetic clutch.

Function sequence, actuation of the PTC heater booster (for diesel engine) 

In vehicles with diesel engine, the PTC heater booster is activated via climate control LIN if required.

Function sequence for actuation of blower motor and rear blower motor (with code (582) Rear air conditioning) 

In accordance with the position of the fresh air/air recirculation flap, the interior air is circulated or fresh air is supplied by actuating the blower motor and the rear blower motor.

The blower motor is actuated by means of the blower regulator and the rear blower motor is actuated by means of the rear air conditioning electronic blower regulator (N29/2) (with code (582) Rear air conditioning), in each case with the power regulated within a range of P = 0 to 100 %.

The blower regulator is actuated via the climate control LIN and the rear air conditioning electronic blower regulator (with code (582) Rear air conditioning) directly by the AAC [KLA] control unit. Depending on the control voltage, the blower regulator regulates the operating voltage for the blower motor from U = 0 to 12.5 V and the rear air conditioning electronic blower regulator (with code (582) Rear air conditioning) regulates the operating voltage for the rear blower motor from U = 0 to 12 V and thus the respective rotational speed from 0 to 100 %.

IMPORTANT With the VCS [SBS] active (without code (526) COMAND with single DVD drive (without navigation)), the blower output is limited.

Air ducting flaps actuation function sequence 

The air distribution in the vehicle interior is controlled by the corresponding adjustment of the air ducting flaps in the air conditioner housing.

The following components are actuated by the AAC [KLA] control unit via climate control LIN:

Right rear center air vent actuator motor (M16/20) (model 221 with code (582) Rear air conditioning)

The left B-pillar air distribution actuator motor (M16/33) (model 221) and the right B-pillar air distribution actuator motor (M16/34) (model 221) are actuated via A/C bus.

Function sequence for actuation of engine and air conditioning electric suction fan with integrated control 

The electric suction fan serves to cool the coolant and refrigerant. The AAC [KLA] control unit calculates the target speed of the electric suction fan depending on the refrigerant pressure and sends the request to the central gateway control unit via interior CAN.

The central gateway control unit forwards the request to the CDI control unit or to the ME-SFI [ME] control unit via chassis CAN. The CDI control unit or the ME-SFI [ME] control unit then calculates the target fan speed depending on the engine temperature and compares it with the automatic air conditioning request. The electric suction fan is then actuated accordingly by the CDI control unit or by the ME-SFI [ME] control unit.

REFER TO SYSTEM WIRING DIAGRAMS Electrical function schematic for automatic air conditioning, input signals Model 216 PE83.40-P-2052-97CAA
    Model 221 PE83.40-P-2052-97SAA
REFER TO SYSTEM WIRING DIAGRAMS Electrical function schematic for automatic air conditioning, actuation Model 216 PE83.40-P-2053-97CAA
    Model 221 PE83.40-P-2053-97SAA
  Component description for instrument cluster A1 GF54.30-P-6000LE
  Component description for COMAND controller unit A40/3
With code (526) COMAND with single DVD drive (without navigation system) or with code (527) COMAND APS with single DVD drive (with navigation system)		 GF82.85-P-3136LE
    With code (529) HIGH Class Japan GF82.85-P-3136LEJ
    With code (530) COMAND APS USA (with navigation system) GF82.85-P-3136LEU
  COMAND display, component description A40/8
Except code (867) SPLITVIEW		 GF54.30-P-6110LE
  Front central operating unit, component description A40/9 GF54.21-P-4500LE
  SPLITVIEW display, component description A40/10
With code (867) SPLITVIEW		 GF54.30-P-6120LE
  Component description for panoramic sliding roof control module A98
Model 221.1 with code (413) Panoramic glass roof with top sliding roof		 GF77.20-P-4106LE
  Component description for CDI control unit N3/9
In model 221 with engine 629		 GF07.16-P-6000OA
    In model 221 with engine 642.8 GF07.16-P-6000OHS
    In model 221 with engine 642.9 GF07.16-P-6000OHL
    In model 221 with engine 651 GF07.16-P-6000OLS
  Component description for ME-SFI [ME] control unit N3/10
With engine 156		 GF07.61-P-6000MAS
    For model 221 with engine 272 (except 272.974) GF07.61-P-6000MIS
    In model 221 with engine 272.974 GF07.61-P-6000MEH
    With engine 273 GF07.61-P-6000MLS
    With engine 275 GF07.61-P-6000MOS
    In model 221 with engine 276 GF07.61-P-6000MMB
    With engine 157, 278. GF07.61-P-6000MMC
  Component description for front SAM control unit with fuse and relay module N10/1 GF54.21-P-6070LE
  Component description for rear SAM control unit with fuse and relay module N10/2 GF54.21-P-6030LE
  Component description for automatic air conditioning control unit N22/1 GF83.40-P-3012LE 
  Rear air conditioning control unit, component description N22/4
Model 221 with code (582) Rear air conditioner		 GF83.50-P-3012LE 
  Rear control unit, component description N22/6
Model 216		 GF54.21-P-4134LA
  Component description for left door control unit N69/1
Model 216		 GF72.29-P-4124LA
  Component description for left front door control unit N69/1
Model 221		 GF72.29-P-4141LE
  Component description for right door control unit N69/2
Model 216		 GF72.29-P-4128LA
  Component description for right front door control unit N69/2
Model 221		 GF72.29-P-4142LE
  Rear door control unit, component description N69/3, N69/4
Model 221		 GF72.29-P-6020LE
  Component description for overhead control panel control unit N70 GF82.20-P-5216LE
  Upper control panel control unit, component description N72/1 GF54.21-P-6040LE
  EZS control unit, component description N73 GF80.57-P-6003LE
  Component description for central gateway control unit N93 GF54.21-P-4170LE
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