GF83.40-P-2004CA Regulation of Automatic Air Conditioning, Function

GF83.40-P-2004CA Regulation of Automatic Air Conditioning, Function
MODEL 207.3/ 4

Function requirements, general
^ Circuit 15 ON
^ Automatic air conditioning switched on
^ Engine running (for cooling operation)
^ Refrigerant compressor (A9) switched on (for cooling mode)
The circuit status of circuit 15 is provided by the electronic ignition lock control unit (N73) via interior CAN (CAN B). The "Engine running" status is provided by the CDI control unit (N3/9) (with diesel engine) or by the ME-SFI [ME] control unit (N3/10) (with gasoline engine) via chassis CAN (CAN E) and routed by the front SAM control unit with fuse and relay module (N10/1) via interior CAN.

Control, general
Electronic control of the temperature and air distribution in the interior is performed depending on the selected settings on the automatic air conditioning control and operating unit (N22/7) and the variables recorded by various sensors (e.g. interior temperature, outside temperature, coolant temperature and vehicle speed). The determination of these variables is described following the description of the adjustments that are relevant for regulation.
The control and operating unit is networked via the interior CAN and the climate control LIN (LIN B8) with the vehicle electronics system. This in turn makes it possible to incorporate relevant parameters in order to improve regulation quality and to lower power consumption.
The automatic air conditioning control function encompasses the following subfunctions:
^ Function sequence for adjustments that are relevant for regulation
^ Function sequence for determining variables
^ Function sequence for AC component actuation

Function sequence for adjustments that are relevant for regulation
The function sequence for the control-relevant settings encompasses the following subfunctions:
^ Function sequence for automatic regulation
^ Function sequence for manual regulation
^ Function sequence for defroster function
^ Function sequence, maximum cooling output (with code (494) USA version)

Additional function requirements, automatic regulation
^ "AUTO" button pressed (light-emitting diode (LED) lights up)

Function sequence for automatic regulation
The regulation of temperature, air distribution, and air volume takes place depending on the temperature preselection on the control and operating unit and the currently existing basic conditions. The air distribution and air volume are set automatically.
In the process, the control and operating unit takes the following variables into account:
- Ambient temperature
- Interior temperature
- Coolant temperature
- Temperature at the air outlets in the vehicle
- Solar radiation on the vehicle
- Vehicle speed
- Temperature on evaporator
- Refrigerant pressure
- Engine speed
- Pollutant concentration of the outside air (with code (581) Comfort automatic air conditioning)
- Dew point temperature (air humidity of the outside air) (up to 31.5.10 with code (581) Comfort automatic air conditioning)
- Temperature and humidity at the windshield (model 207.3 as of 1.12.09, model 207.4)
- Door status
- Side window position
- Panorama roof position (with code (413) Panoramic glass sunroof with top sliding sunroof)
- Settings on rear automatic air conditioning operating unit (N22/4) (with code (581) Comfort automatic air conditioning)
- Status of the voice control system (VCS [SBS]) (with code (511) Audio 50 APS with DVD changer or with code (512) COMAND APS with DVD changer or with code (527) COMAND APS with single DVD drive (with navigation))
- Status of the soft top (model 207.4)

Additional function requirements, manual regulation
^ Air distribution and air volume changed manually (LED in "AUTO" button does not light up)

Function sequence for manual regulation
The regulation of temperature, air distribution, and air volume takes place depending on the temperature selections made on the control and operating unit and the currently existing basic conditions. The control and operating unit takes the same variables into consideration as with automatic control.
By pressing the "ZONE" button, the values for air distribution and temperature set on the driver side are adopted for the passenger side; for the rear area, only the temperature values are adopted. The LED goes out when the function is activated. If the temperature on the passenger side or in the rear is adjusted manually, the LED lights up. Multizone temperature control in the vehicle is thus shown.

Additional function requirements, defroster function
^ Defroster button pressed (LED is on)

Function sequence of defroster function
When the "defrost" button is pressed, all air flaps of the air conditioner housing are closed with the exception of the defroster flaps and the fresh air/recirculated air flap. These are fully opened.
The defroster flaps are adjusted so that the maximum air flow is directed to the windshield and the front side windows. The blend air flaps are set to full warm air supply.
The blower motor (A32m1) is actuated by the control and operating 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.
With code (581) Comfort automatic air conditioning, defrosting takes place separately by the left defroster flap actuator motor (M2/8) for the driver and by the right defroster flap actuator motor (M2/9) for the front passenger. Without code (581) Comfort automatic air conditioning, the regulation for the driver and the front passenger takes place together through the defroster flap actuator motor (M2/16).

Additional function requirements, maximum cooling output (with code (494) USA version)
^ "MAX COOL" button actuated (LED lights up)

Function sequence, maximum cooling output (with code (494) USA version)
Pressing the "MAX COOL" button, raises the blower output to 100%. "MAX COOL" is shown on the display.

Function sequence, determining variables
The function sequence for determining the variables encompasses the following subfunctions:
^ Function sequence for determining the outside temperature
^ Function sequence for determining the interior temperature
^ Function sequence for determining the coolant temperature
^ Function sequence for determining the temperature at the air outlets in the vehicle
^ Function sequence for determining the solar radiation on the vehicle
^ Function sequence for determining the vehicle speed
^ Function sequence for determining the temperature at the evaporator
^ Function sequence for determining the refrigerant pressure
^ Function sequence for determining the engine speed
^ Function sequence for determining the door status
^ Function sequence for determining side window position
^ Function sequence for determination of panoramic roof position (with code (413) Panoramic glass sunroof with top sliding sunroof)
^ Function sequence for determining the pollutant concentration of the outside air (with code (581) Comfort automatic air conditioning)
^ Function sequence for determining dew point temperature up to 31.5.10 (with code (581) Comfort automatic air conditioning)
^ Function sequence for determining temperature and humidity at the windshield (as of 1.12.09 with model 207.3, model 207.4)
^ Function sequence for determining settings on rear automatic air conditioning operating unit (with code (581) Comfort automatic air conditioning)
^ Function sequence for determination of VCS status (with code (511) Audio 50 APS incl. DVD changer or with code (512) COMAND APS incl. DVD changer or with code (527) COMAND APS with single DVD drive (with navigation))
^ Function sequence for determining the soft top status (model 207.4)

Function sequence for determining the outside temperature
The outside temperature sensor (B14) measures the outside temperature. The temperature value is read in directly by the front SAM and transmitted via interior CAN to the control and operating unit. The control and operating unit needs this value to reach the desired interior temperature by adjusting the blend air flaps accordingly.
If the vehicle is stationary, the measured temperature can differ considerably from the outside temperature. The outside temperature is therefore only included in the control if the vehicle speed is v 20 km/h.
The previously measured temperature is used at speeds of v < 20 km/h and when the ignition is being switched on and off.

Function sequence for determining the interior temperature
The interior temperature is sensed in the instrument panel area by the interior temperature sensor (B10/4) and is read in directly by the control and operating unit.
In addition, the interior temperature is recorded by the interior temperature sensor with integrated fan (N70/3b1) in the roof area and sent directly to the control and operating unit.
Each of the two in-car air temperature sensors is equipped with a ventilation blower that draws the air in from the vehicle interior for the temperature measurement.
The ventilation blower enables the constant circulation at the in- car temperature sensors, which guarantees a high level of temperature measurement accuracy and achieves temperature control that is as independent of the airflow ratios in the interior as possible.
A mean value is calculated from the measurements of the in-car temperature sensors. Together with the value of the outside temperature sensor, the mean value is compared to a characteristics map stored in the control and operating unit and used to control the interior temperature.
With an open window or open door, the mean value of the interior temperature is retained by the control and operating unit and immediate further operation of the air conditioning with the set specified temperature is guaranteed.

Function sequence for determining the coolant temperature
The coolant temperature is recorded by the coolant temperature sensor (B11/4). The temperature value is read in by the CDI control unit or ME-SFI control unit and transmitted to the front SAM control unit via the chassis CAN.
It transmits the value to the control and operating unit via interior CAN.
The value is used for control of blend air flaps, PTC heater booster (R22/3) (with engine 271.8, 642.8 or 651.9) and for actuation of the coolant circulation pump (M13/5) (with code (581) comfort automatic air conditioning ).

Function sequence for determining the temperature at the air outlets in the vehicle
The temperature on the air outlets is sensed by the left side air vent temperature sensor (B10/31), right side air vent temperature sensor (B10/32), left front footwell vent temperature sensor (B10/35) and right front footwell vent temperature sensor (B10/36).
The temperature sensors are read in directly by the control and operating unit. The control and operating unit regulates the outlet air temperature of the particular air outlets.
In vehicles up to 31.5.11 with code (581) Comfort automatic air conditioning, the rear footwell vent air outlet temperature sensor (B10/38) is installed additionally at the rear air outlet.

Function sequence for determining the solar radiation on the vehicle
The control and operating unit uses the sun sensor (B32/3) to record the angle of incidence and the intensity of the solar radiation on the vehicle. The interior temperature and the blower speed are adjusted in accordance with the measurements.
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 for determining the vehicle speed
The vehicle speed is transmitted by the instrument cluster (A1) to the control and operating unit via interior CAN.
The vehicle speed is used to control the ram air function (with code (581) Comfort automatic air conditioning) and for internal calculation of the outside temperature, e.g. when in stationary operation.

Function sequence for determining the temperature at the evaporator
To prevent any icing-up of the evaporator, the temperature there is recorded by the evaporator temperature sensor (B10/6) and read in directly by the control and operating unit.
If the evaporator temperature drops to approx. T = 2°C, the refrigerant compressor is switched off.

Function sequence for determining the refrigerant pressure
The refrigerant pressure is recorded by the refrigerant pressure sensor (B12). The pressure is compared to a temperature/pressure curve stored in the control and operating unit. At a refrigerant pressure p < 1.7 bar and p > 30 bar, the refrigerant compressor is switched off.
The refrigerant pressure sensor is read in directly by the front SAM control unit and the read in value is sent via interior CAN to the control and operating unit.

Function sequence for determining the engine speed
The engine speed is registered by the CDI control unit or the ME-SFI [ME] control unit and sent over the chassis CAN to the front SAM control unit. It transmits the value to the control and operating unit via interior CAN. The engine speed is used among others to regulate the refrigerant compressor.

Function sequence for determining the door status
The open and closed statuses at the corresponding door are recorded by the left front door rotary tumbler switch (A85s1) and the right front door rotary tumbler switch (A85/1s1) The status of the left front door rotary tumbler switch is read in by the left front door control unit (N69/1) and the status of the right front door rotary tumbler switch by the right front door control unit (N69/2).
The values are transmitted to the control and operating unit via the interior CAN.
The control and operating unit retains the current blower output when the door is open in order to prevent unnecessary readjustment in the event of high temperature differences between the inside and outside air.

Function sequence for determining side window position
The corresponding side window position is determined by the left front door control unit and right front door control unit of by the rear control unit (N22/6) and sent to the control and operating unit via interior CAN.

Function sequence for determination of panoramic roof position (with code (413) Panoramic glass sunroof with top sliding sunroof)
The position of the panoramic glass roof is read in by the panoramic sliding roof control module (A98) and transmitted to the control and operating unit via the interior CAN.

Function sequence for determining the pollutant concentration of the outside air (with code (581) Comfort automatic air conditioning)
The pollutant sensor (B31) measures the concentration of the pollutants carbon monoxide (CO) and nitrogen oxide (NO X).
The values are read in directly by the control and operating unit over the climate control LIN. The control and operating unit controls the automatic recirculation according to the read in values.

Function sequence, determining the dew point temperature (up to 31.5.10) with code (581) Comfort automatic air conditioning
The dew point sensor (B11/12) uses the ambient temperature and the air humidity to calculate the dew point and transmits it to the control and operating unit via climate control LIN.
When the dew point is reached, the windows and the outside mirrors start to fog up. In order to prevent this, the air conditioning, heated outside mirror and rear window heater (R1) are activated.

Function sequence for determining temperature and humidity at the windshield (as of 1.12.09 with model 207.3, model 207.4)
The 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 interior humidity/temperature sensor sends a signal to the control and operating unit via the climate control LIN.
In vehicles with code (B03) ECO start/stop function, the control and operating unit sends the "Engine start" request to the CDI control unit or the ME-SFI [ME] control unit so that the engine is started, the refrigerant compressor runs and thus prevents the windshield from fogging up.
The exact measurement process enables activation of the measures as late as possible, but as early as necessary.

Function sequence for determining settings on rear automatic air conditioning operating unit (with code (581) Comfort automatic air conditioning)
The rear compartment climate control functions can be adjusted by the rear passengers using the rear automatic air conditioning control unit. Operation of the temperature rockers in the rear automatic air conditioning operating unit is read in and processed by the control and operating unit via the climate control LIN.
Using this data, the temperature in the rear is controlled using the rear blend air flap actuator motor (M2/35). Actuation is performed by the control and operating unit via the climate control LIN.

Function sequence for determination of VCS status (with code (511) Audio 50 APS incl. DVD changer or with code (512) COMAND APS incl. DVD changer or with code (527) COMAND APS with single DVD drive (with navigation))
With active voice control system, the blower output of the blower regulator is limited.
The radio with auto pilot system (A2/56) (with code (511) Audio 50 APS incl. DVD changer or the COMAND controller unit (A40/3) (with code (512) COMAND APS with DVD changer or with code (527) COMAND APS with single DVD drive (with navigation)) sends the voice control system status over the interior CAN to the control and operating unit.

Function sequence for determining the soft top status (model 207.4)
The rear control unit transmits the soft top status via interior CAN to the control and operating unit.

Function sequence for AC component actuation
The function sequence for actuating the A/C components encompasses the following subfunctions:
^ Function sequence for actuation of refrigerant compressor
^ Function sequence for actuation of blower motor
^ Function sequence for actuating PTC heater booster (with engine 271.8, 642.8 or 651.9)
^ Function sequence for actuation of the air ducting flaps
^ Function sequence for actuating internal combustion engine fan motor and air conditioning with integrated control (M4/7)

Function sequence for actuation of refrigerant compressor
The refrigerant compressor is responsible for induction and compression of the refrigerant.
The refrigerant compressor output is regulated continuously up to 100 % by the control and operating unit via the compressor control valve. The control and operating unit transmits the switch-on request via the interior CAN to the front SAM control unit. This receives the request and actuates the compressor control valve.
In vehicles as of 1.6.10 with engine 651.911 and in vehicles with engine 271, 276 and as of 1.6.11 with engine 651, a refrigerant compressor with refrigerant compressor magnetic clutch (A9y1) is installed. To prevent the refrigerant compressor from turning with the air conditioning switched off, the refrigerant compressor is disconnected from the belt drive by means of the refrigerant compressor magnetic clutch. This saves fuel. The control and operating unit sends the request to the front SAM control unit via the interior CAN. This directly actuates the refrigerant compressor magnetic clutch.

Function sequence for actuation of blower motor
Ventilation is achieved with the aid of the blower motor. The control and operating unit forwards the request to the blower regulator, which then actuates the blower motor.
With VCS [SBS] active, the blower output is limited.

Function sequence for actuating PTC heater booster (with engine 271.8, 642.8 or 651.9)
The PTC heater booster is switched on by the climate control LIN if required

Air ducting flaps actuation function sequence
The air distribution in the vehicle interior is controlled by corresponding adjustment of the air duct flaps in the air conditioning housing.
The control and operating unit actuates the following components over the climate control LIN:
Vehicles without code (581) Comfort automatic air conditioning:
- for fresh air/recirculated air control:
- Fresh air/recirculated air flap actuator motor (M2/5)
- for temperature control:
- Left blend air flap actuator motor (M2/6)
- Right blend air flap actuator motor(M2/7)
- for ventilation control:
- Defroster flap actuator motor
- Air distribution flap actuator motor(M16/22)
Vehicles with code (581) Comfort automatic air conditioning:
- for fresh air/recirculated air control:
- Fresh air/recirculated air flap actuator motor
- for temperature control:
- Left blend air flap actuator motor
- Right blend air flap actuator motor
- Rear blend air flap actuator motor
- for ventilation control:
- Left defroster flap actuator motor
- Right defroster flap actuator motor
- Left foot well flap actuator motor(M2/10)
- Right foot well flap actuator motor(M2/11)
- Left center air vent flap actuator motor(M2/12)
- Right center air vent flap actuator motor(M2/13)
- Diffuser flap actuator motor(M2/21)
- For ram air control:
- Ram air flap actuator motor(M2/34)(upto31.5.10)
- Fresh air/recirculated air flap actuator motor(asof1.6.10)

Function sequence for actuating internal combustion engine fan motor and air conditioning with integrated control
The fan motor is used for cooling the coolant and refrigerant.
The control and operating unit calculates the specified fan speed depending on the refrigerant pressure and transmits the request to the front SAM control unit over the interior CAN. This sends the request to the CDI control unit or the ME-SFI [ME] control unit over the chassis CAN.
The CDI control unit or ME-SFI [ME] control unit then calculates the specified fan speed based on the engine temperature and compares this with the request from the control and operating unit.
The fan motor is actuated accordingly.