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Climate Control Regulation, Function - GF83.40-P-2012GWM

Model 463 (except 463.342) 

as of model year 2019 

G13659966Courtesy of MERCEDES-BENZ USA

Function requirements, general 

For regulating the climate control:

IMPORTANT The electronic ignition lock control unit sends the status of terminal 15 via interior CAN to the A/C control unit.

IMPORTANT The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" signal over the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and the interior CAN to the climate control, control unit.

Climate control, general 

The electronic temperature control and the air distribution in the vehicle interior takes place dependent on the selected settings on the air conditioning control panel, on the rear climate control operating unit or in the head unit and the variables recorded by the various sensors (e.g. vehicle interior temperature, outside temperature, coolant temperature, vehicle speed).

The A/C control unit is networked over the interior CAN, climate control LIN 1, climate control LIN 2 and the A/C operating unit LIN to the vehicle electronics. This in turn makes it possible to incorporate relevant parameters in order to improve regulation quality and to lower power consumption.

The climate control regulation function encompasses the following subfunctions:

Recording and evaluation of variables 

The following variables are recorded and evaluated:

Outside temperature 

The outside temperature sensor measures the outside temperature.

The front SAM control unit reads in the signal of the outside temperature sensor directly, calculates the outside temperature and transmits it to the A/C control unit over the interior CAN. The climate control, control unit regulates the interior temperature according to the outside temperature by adjusting the blend air flaps.

IMPORTANT If the vehicle is stationary, the measured temperature can differ considerably from the actual outside temperature. The outside temperature is only included in the regulation of the vehicle interior temperature when the vehicle speed for a period of at least 30 s is higher than 30 km/h. At speeds <30 km/h as well as when switching the ignition on and off, the last measured temperature value is then used.

Interior temperature in head area 

The interior temperature in the head area is recorded by the interior temperature sensor with the integrated fan that is incorporated into the overhead control panel control unit. The integrated fan of the interior temperature sensor draws the air for temperature measurement out of the vehicle interior. The overhead control panel control unit reads in the value of the interior temperature and transmits this via the interior CAN to the climate control, control unit.

Interior temperature in instrument panel area 

The interior temperature in the instrument panel area is recorded by the interior temperature sensor. The interior temperature sensor is read in directly by the climate control, control unit.

Temperature at the air outlets in the vehicle 

The temperatures at the air outlets in the vehicle are recorded by the air outlet temperature sensors. The signals from the air outlet temperature sensors are read in directly by the climate control, control unit. The A/C system control unit regulates the air outlet temperature at each of the air outlets.

Temperature and moisture on windshield 

A humidity and temperature sensor is integrated in the rain/light sensor with additional functions. This sensor measures the relative air humidity and temperature directly at the inside of the windshield.

These values are used by the rain/light sensor with additional functions to calculate the dew point temperature. Comparison of the windshield surface temperature with the dew point temperature enables impending fogging of the windows to be detected.

The rain/light sensor with additional functions sends the dew point temperature via the rain/light sensor LIN, front SAM control unit and interior CAN to the climate control, control unit.

If the probability of window fogging is high, the climate control, control unit increases the blower setting. If the automatic ECO start/stop function is active, the climate control, control unit can prevent an automatic engine stop. In the case of impending window fogging during an engine stop phase, the climate control, control unit can cause the engine to start and the refrigerant compressor to switch in.

Coolant temperature 

The coolant temperature is calculated by the CDI control unit or by the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit sends the coolant temperature via the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and interior CAN to the climate control, control unit.

The coolant temperature is used to control the blend air flaps and to actuate the coolant circulation pump.

Evaporator temperature 

The temperature at the evaporator is recorded by the evaporator temperature sensor. The A/C control unit reads in the signals from the evaporator temperature sensor directly. If the evaporator temperature drops to approx. 2 °C, the refrigerant compressor is switched off. This serves to prevent the evaporator from icing up. As of an evaporator temperature of 2.5 °C, the refrigerant compressor is switched on again.

The evaporator temperature is held for a maximum of 20 minutes at 2.5 °C. The evaporator temperature is then adjusted to a range between 3 and 8 °C (depending on the cooling output requirement).

Refrigerant pressure 

The refrigerant pressure is recorded by the refrigerant pressure sensor. The climate control, control unit reads in the signals from the refrigerant pressure sensor directly. The pressure is compared with a stored temperature/pressure curve. At a refrigerant pressure <0.8 or > 28 bar, the refrigerant compressor is switched off or not switched on.

Solar radiation 

A sun sensor (2-quadrant sensor) is integrated in the rain/light sensor with additional functions. The sun sensor detects the angle of incidence and the intensity of the solar radiation entering the left and right side of the vehicle. The rain/light sensor with additional functions sends this information via the rain/light sensor LIN, front SAM control unit and interior CAN to the climate control, control unit. The climate control, control unit then regulates the interior temperature accordingly.

For example, in the event of one-sided solar radiation, an appropriate temperature difference is set between the left and the right specified control temperatures.

If the sun is shining into the vehicle from the side or from the rear and additionally at an acute angle, the sun sensor at the windshield would deliver imprecise values. This is why a sun sensor is virtually realized in the rear passenger compartment. Location information is obtained from GPS data. The position of the sun is deduced from the time of day. The head unit sends the relevant information via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control, control unit. The climate control unit references the values from the sun sensor at the windshield and adapts the temperature control accordingly.

Air quality 

The air quality sensor measures the concentration of the following pollutants:

The climate control, control unit reads in the signals from the air quality sensor via the climate control LIN 1. If the concentration of pollutant gas is high, the climate control, control unit activates air recirculation mode.

Vehicle speed 

The vehicle speed is calculated by the instrument cluster. Information about the vehicle speed is transmitted by the instrument cluster via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control, control unit. The vehicle speed is used for regulation of the ram air function and for internal calculation of the outside temperature, e.g. in stationary operation.

Engine speed 

The engine speed is calculated by the CDI control unit or the ME-SFI [ME] control unit. The CDI control unit or the ME-SFI [ME] control unit sends the engine speed via the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and interior CAN to the climate control, control unit. The engine speed is used to regulate the refrigerant compressor, among other things.

Door status 

The status of each door (open or closed) is determined by the following control units and sent via the interior CAN to the climate control, control unit:

If the door is open, the climate control, control unit references the values from the interior temperature sensor with integrated fan and adapts the temperature control accordingly. If there is a large difference in temperature between the interior air and outside air, unnecessary readjustment is avoided.

Position of side windows 

The position of the side windows is determined by the following control units and sent via the interior CAN to the climate control, control unit:

If the side windows are open, the climate control, control unit references the values from the interior temperature sensor with integrated fan and adapts the temperature control accordingly. If there is a large difference in temperature between the interior air and outside air, unnecessary readjustment is avoided.

Position of sliding roof (with code F15 (Sliding roof)) 

The position of the sliding roof is transmitted by the sliding roof control module to the A/C control unit via the interior CAN.

If the sliding sunroof is open, the climate control, control unit references the values from the interior temperature sensor with integrated fan and adapts the temperature control accordingly. If there is a large difference in temperature between the interior air and outside air, unnecessary readjustment is avoided.

Operating settings 

The settings for climate control of the vehicle interior can be made at the following control points:

Climate control operating unit 

The climate control operating unit has the following buttons which are used for making the various settings:

The climate control operating unit sends information regarding the settings via the climate control LIN to the climate control, control unit.

This data is used to regulate the air flow, air distribution and interior temperature. The selected settings are additionally displayed on the Audio/COMAND display. For this purpose, the climate control, control unit sends the relevant information via the interior CAN, the electronic ignition lock control unit and the user interface CAN to the head unit.

The head unit generates the corresponding image data, transmits a switch-on request via the telematics CAN to the audio/COMAND display and transfers the image data via the HSVL line to the audio/COMAND display. For feedback on the function, the A/C control unit transmits the request for LED actuation via the climate control LIN to the climate control operating unit.

IMPORTANT The air conditioning system or the refrigerant compressor can be switched off if the "A/C" button (except code H12 (Stationary heater)) is installed. If this button is not installed, they can only be switched off via the head unit menu.

Rear air conditioning operating unit 

Settings for climate control in the rear compartment can be made at the rear air conditioning operating unit. The rear air conditioning operating unit sends information regarding the settings via the climate control LIN to the climate control, control unit. This data is used to regulate the air volume and the temperature in the rear compartment.

The settings are shown in the display of the rear air conditioning operating unit.

Head unit 

The menu in the head unit can be used to switch off the air conditioning system or to select the climate control function. The head unit sends the relevant information via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control, control unit. The head unit generates the corresponding image data, transmits a switch-on request via the telematics CAN to the audio/COMAND display and transfers the image data via the HSVL line to the audio/COMAND display.

VCS 

With the VCS, various functions of the air conditioning system can be operated via voice input (e.g. the vehicle interior temperature). The VCS is integrated in the head unit. The head unit sends the relevant information via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control, control unit.

VCS status 

When the VCS is active, the output of the electronic blower motor is limited by the climate control, control unit. The head unit sends the status of the VCS over the user interface CAN, electronic ignition lock control unit and the interior CAN to the A/C control unit.

Actuation of air conditioning components 

The function sequence for actuating the A/C components encompasses the following subfunctions:

Actuation of electronic blower motor 

Ventilation of the vehicle interior is achieved with the aid of the electronic blower motor. The climate control, control unit actuates the electronic blower motor via climate control LIN 2.

IMPORTANT The electronic blower motor drives a radial blower which circulates the air in the vehicle interior or supplies fresh air to the vehicle interior.

This prevents the windows from fogging up, supplies air to the vehicle occupants and allows pleasant and constant temperatures to be reached quickly in the vehicle interior. Depending on the current settings at climate control operating unit, the air is distributed via various air ducts and air outlets in the vehicle interior.

IMPORTANT With VCS [SBS] active, the blower setting is reduced.

IMPORTANT The electronic blower motor is switched off in the event of an accident (crash signal transmitted).

Actuation of rear blower motor 

The rear blower motor is used for better ventilation of the rear passenger compartment. The climate control, control unit actuates the rear blower motor over the climate control LIN 2. Actuation takes place depending on the settings made at the rear air conditioning operating unit.

IMPORTANT If the rear blower motor is switched on, the electronic blower motor is also actuated.

IMPORTANT The rear blower motor is switched off in the event of an accident (crash signal sent).

Actuation of air ducting flaps 

The air distribution in the vehicle interior is controlled by adjusting the air ducting flaps in the air conditioner housing. The following components are actuated by the A/C control unit via climate control LIN 1:

G13659967Courtesy of MERCEDES-BENZ USA

Air outlets in the vehicle interior 

IMPORTANT There are additional air outlets in the B-pillar trim.

Actuation of refrigerant compressor 

Engine 176 177 

The refrigerant compressor is responsible for induction and compression of the refrigerant. The refrigerant compressor is continuously output-controlled up to 100 % by the climate control, control unit through the refrigerant compressor regulation valve. The A/C system control unit actuates the refrigerant compressor regulating valve directly.

Engine 656 

A magnetic clutch is also installed. This can be used to completely disconnect the refrigerant compressor from the belt drive power flow.

This in turn enables additional fuel savings to be made. The A/C control unit directly actuates the refrigerant compressor with magnetic clutch.

IMPORTANT In the event of an accident (crash signal sent), the refrigerant compressor is switched off via the refrigerant compressor regulation valve.

In addition, the climate control, control unit sends the calculated torque of the refrigerant compressor via the interior CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drivetrain CAN to the CDI control unit or to the ME-SFI [ME] control unit. This keeps the idle speed constant in accordance with the additional load that occurs when the refrigerant compressor is switched on.

The refrigerant compressor is switched off under the following conditions:

Actuation of fan motor (engine fan) 

The fan motor is used for cooling the coolant and refrigerant. The climate control, control unit calculates the specified fan speed depending on the refrigerant pressure and sends this over the interior CAN, electronic ignition lock control unit and the suspension FlexRay to the powertrain control unit.

The powertrain control unit corrects the requested fan speed to match the engine temperature and regulates the fan motor over the drivetrain LIN accordingly.

Actuation of PTC heater booster (engine 656) 

When required, the PTC heater booster is switched on by the A/C control unit over the climate control LIN 2. As a result, the vehicle interior is heated up more quickly.

IMPORTANT The PTC heater booster is switched off in the event of an accident (crash signal transmitted).

Actuation of coolant circulation pump 

The coolant circulation pump is used to support the coolant circuit. The heated coolant passes through the heater heat exchanger, which dissipates heat to the air blowing by. At low engine speed or during engine stop, the coolant circulation pump is also actuated to ensure that the flow volume needed to heat up the air flowing past is adequate. The climate control, control unit actuates the coolant circulation pump directly.

Additional function requirements for actuation of driver side air vent ionizer (with code HA1 (Fresh air package)) 

Actuation of the driver side air vent ionizer (with code HA1 (Fresh air package)) 

The driver side air vent ionizer is used for ionization of the air in the vehicle interior. The air is cleaned and freshened by means of ionization. The ionization of the interior air itself is odor-neutral and cannot be detected directly as such in the vehicle.

The head unit transmits the "Switch on ionization" request via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control, control unit. The A/C control unit actuates the driver side air vent ionizer via climate control LIN 2.

Shift point adjustment 

If increased cooling or heating is required, the fully integrated transmission control unit can adjust the shift point.

The A/C control unit sends the shift point adjustment request over the interior CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit and the drive train CAN to the fully integrated transmission control unit.

Fresh air mode 

The fresh air/ram air/air recirculation flap is open during fresh air mode.

Fresh air is fed through the air conditioning housing and into the vehicle interior.

The climate control, control unit actuates the fresh air/ram air/air recirculation flap actuator motor via climate control LIN 1.

Recirculated air mode 

The function sequence for the air recirculation mode encompasses the following subfunctions:

Air recirculation mode via the air recirculation mode button 

Pressing the air recirculation mode button on the climate control operating unit for less than 1.5 s closes the fresh air/ram air/air recirculation flap to prevent air entering from the outside. The air only circulates in the vehicle interior and unpleasant odors and harmful gases are kept out. The LED in the air recirculation mode button lights up during air recirculation mode.

The climate control operating unit reads in the status of the air recirculation mode button directly and sends the status to the climate control, control unit via the climate control LIN. The climate control, control unit actuates the fresh air/ram air/air recirculation flap actuator motor via the air conditioning control LIN 1 and transmits the "Air-recirculation mode active" status via the air conditioning control LIN 1 to the air conditioning control panel which actuates the LED in the air-recirculation mode button.

The air recirculation mode is switched off automatically:

Vehicles except code ZU7 (Canada national version) or code ZU8 (USA national version) or code ZW4 (South Korea national version): If the air-recirculation mode button is operated for > 1.5 s, the side windows and the sliding roof (with code F15 (Sliding roof)) are closed.

If the air-recirculation mode button is then operated for > 1.5 s, the side windows and the sliding roof (with code F15 (Sliding roof)) are moved to their default positions (provided that they were not manually adjusted during air-recirculation mode).

Additional function requirements for pollutant- controlled air recirculation mode 

The air quality sensor sends the outside air pollutant values over the climate control LIN 1 to the A/C control unit. Starting from a certain pollutant concentration, the fresh air/ram air/recirculated air flap is automatically set to the recirculated air position. Outside air supply is prevented and only the inside air is recirculated. If, after starting the engine, the condition for pollutant-sensitive air recirculation mode is given, fresh air is initially supplied for 30 s. Then 80 % of the pollutant-controlled air recirculation mode is initially used. After 10 s the output is increased as required to the 100 % pollutant controlled air-recirculation mode.

IMPORTANT The pollutant-controlled air-recirculation mode is active for a maximum of 30 minutes and this is not indicated by the LED in the air-recirculation mode button.

Additional function requirements for automatic air recirculation mode 

Automatic air recirculation mode 

The air recirculation mode is switched on automatically:

The head unit sends the GPS data via user interface CAN, electronic ignition lock control unit and interior CAN to the A/C control unit.

The A/C control unit actuates the fresh air/ram air/air recirculation flap actuator motor over the climate control LIN 1 and the fresh air/ram air/air recirculation flap is set to the recirculated air position.

IMPORTANT The automatic air-recirculation mode active for a maximum of 30 minutes and this is not indicated by the LED in the air-recirculation mode button.

Defrost 

Operating the defrosting button causes all the air flaps with the exception of the defroster flap and the fresh air/ram air/air recirculation flap to be closed. These are fully opened. The defroster flap is 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 climate control, control unit actuates the electronic blower motor via climate control LIN 2 in such a way that optimum defrost operation is guaranteed depending on the outflowing air temperature.

The refrigerant compressor is activated in order to ensure that the air flowing out is dried. The air is dried and then heated up to the maximum temperature.

Additional function requirements for evaporator drying process 

Evaporator drying 

To counteract odors in the vehicle interior and fogging of windows when the air conditioning system is started, evaporator drying is carried out.

After the engine is switched off, the climate control, control unit sends the signal to activate the evaporator drying timer via the interior CAN, the electronic ignition lock control unit and the user interface CAN to the instrument cluster. The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" signal over the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and the interior CAN to the climate control, control unit.

After a waiting time of 1 h, the instrument cluster sends the request for evaporator drying via the user interface CAN, electronic ignition lock control unit and interior CAN to the climate control, control unit, which starts the evaporator drying process. For this purpose, the electronic blower motor is actuated at the lowest stage for 30 min. The climate control, control unit actuates the electronic blower motor via climate control LIN 2. The air supply serves to reduce residual moisture in the evaporator.

Residual heat utilization (with code H12 (Stationary heater)) 

The residual heat utilization function is switched on by operating the climate control menu and residual heat ON/OFF button on the air conditioning control panel. The A/C control unit reads in the control signals of the climate control operating unit via climate control LIN and actuates the coolant circulation pump directly. The coolant circulation pump delivers the still warm (residual heat) coolant through the heat exchanger.

The climate control, control unit actuates the electronic blower motor via climate control LIN 2 at the same time. The intake air from the electronic blower motor is routed past the heater heat exchanger and heated up in the process. The function is terminated after 30 min or when the on-board electrical system voltage drops below a certain value.

Shutoff of air conditioning after an accident (crash signal sent) 

In order to prevent harmful gases entering the vehicle interior after an accident, the climate control, control unit starts the following activities:

The supplemental restraint system control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the A/C control unit.

IMPORTANT Detailed information on actuation of the individual components in the air conditioning is available in the "Actuating the A/C components" chapter.

  Electrical function schematic for climate control input signals   PE83.40-P-2056-97ZGB
  Electrical function schematic for climate control actuation   PE83.40-P-2057-97ZGB
  Overview of system components for climate control   GF83.40-P-9994GWM 
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