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

MODEL 453.091/391/491 

G12097002Courtesy of MERCEDES-BENZ USA

Shown on model 453.0/3 with code I01 (Automatic air conditioning system) 

Function requirements, general 

For cooling mode (only vehicles with code I01 (Automatic air conditioning)):

IMPORTANT The center SAM control unit activates the air conditioning system power supply solenoid switch with circuit 15 ON. The circuit 15 status of the ignition lock is received by the center SAM control unit over a direct line from the vehicle interior fuse and relay module.

The electric drive control unit transmits the "Drivetrain operational" signal via the interior CAN to the climate control unit.

Climate control, general 

In vehicles with code I01 (Automatic air conditioning), the electronic temperature control and the air distribution in the vehicle interior take place depending on the settings made at the climate control operating unit and variables recorded via various sensors (e.g. interior temperature, outside temperature, vehicle speed). Determination of these variables is described below. The air distribution and blower settings of the blower motor are controlled automatically in "AUTO" mode.

In vehicles without code I01 (Automatic air conditioning), the temperature and the air distribution in the vehicle interior is controlled independently of the interior temperature, outside temperature and vehicle speed variables. The interior temperature and air distribution are controlled purely according to the setting (warmer or colder) at the climate control operating unit. The blower motor is actuated or controlled using electricity only in accordance with the blower setting made.

IMPORTANT Detailed information about possible settings is available in the separate component description for the "Climate control operating unit". The climate control unit is networked with the vehicle electronics via the interior CAN, the telematics CAN and the climate control LIN.

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:

Function sequence for recording and evaluating variables 

The following variables are recorded and evaluated. Depending on the A/C system installed, these have an influence on the regulation of the climate control:

The outside temperature sensor measures the outside temperature. The instrument cluster reads in the outside temperature sensor signal directly, calculates the outside temperature and sends this via the interior CAN to the climate control unit, which then uses the outside temperature value to regulate the refrigerant compressor.

The climate control unit receives the outside temperature via the interior CAN. The A/C control unit requires this value to achieve the required interior temperature by adjusting the blend air flaps accordingly.

IMPORTANT If the vehicle is stationary, the measured temperature can differ considerably from the outside temperature. This is why the outside temperature is only taken account for the regulation, if the vehicle speed was more than v = 30 km/h for a period of at least t = 30 s. At speeds of v < 30 km/h as well as when switching the ignition on and off, the temperature value measured last is used.

Temperature in vehicle interior and moisture on windshield variable (only vehicles with code l01 (Automatic air conditioning)) 

The vehicle interior humidity and temperature sensor measures the relative humidity and temperature in the vehicle interior directly at the inside of the windshield and uses this to determine the dew point temperature. The surface temperature of the windshield and the interior temperature are also determined. The comparison with the dew point temperature enables any (impending) fogging of the windshield to be detected. The signals of the vehicle interior humidity and temperature sensor are read in directly by the climate control unit.

If the windshield threatens to fog up, corresponding countermeasures are taken such as switching in the refrigerant compressor.

Evaporator temperature variable (only vehicles with code l01 (Automatic air conditioning)) 

To prevent the evaporator from icing up, the temperature there is recorded by the evaporator temperature sensor. The signals from the evaporator temperature sensor are read in and evaluated directly, with code I01 (Automatic air conditioning), by the climate control unit. The control of the electric refrigerant compressor is adapted in accordance with the evaporator temperature. If the evaporator temperature drops to approx. T = 2 °C, the electric refrigerant compressor is switched off. To do so, the climate control unit transmits the relevant signals for switching on or off and controlling the rpm via the interior CAN to the powertrain control unit.

Refrigerant pressure variable (only vehicles with code l01 (Automatic air conditioning)) 

The refrigerant pressure is recorded by the coolant pressure sensor. The signals of the coolant pressure sensor are read in directly by the electric drive control unit. The pressure is compared with a stored temperature/pressure curve. The refrigerant compressor is switched off or not switched in at a refrigerant pressure of p < 0.8 bar and p > 30 bar.

The refrigerant compressor is switched in again from a refrigerant pressure of p > 0.9 bar.

Solar radiation variable (only vehicles with code l01 (Automatic air conditioning)) 

The angle of incidence and the intensity of the solar radiation in the vehicle are recorded by the sun sensor in the rain/light sensor. The rain/light sensor reads in the signals from the sun sensor directly, evaluates them and forwards information about the solar radiation over the rain/light sensor LIN, driver-side SAM control unit and the interior CAN to the climate control unit. The blowing air temperature and the blower speed are adjusted in accordance with the values.

Vehicle speed variable (only vehicles with code l01 (Automatic air conditioning)) 

The vehicle speed is transmitted by the Electronic Stability Program control unit via the interior CAN to the electric drive control unit and the climate control unit. It is used for internal computation of the outside temperature, e.g. when in stationary mode and also for regulation of the fan, depending on the vehicle speed.

The vehicle speed is also used to control the ram air function.

Settings at the climate control operating unit 

The climate control of the vehicle interior can be adjusted using the following buttons at the climate control operating unit:

The settings are transmitted by the climate control operating unit via the climate control LIN to the A/C control unit where they are processed. The data are used to regulate the air volume, air distribution and temperature. In order to provide feedback about the function, the climate control unit transmits the request for actuating the LED of the relevant button via the climate control LIN to the climate control operating unit.

In vehicles with code 535 (smart media system) and with code I01 (Automatic air conditioning), the icon of the heater or the icon for the climate control and the current energy flow is displayed on the touchscreen (A40/3p1) of the smart radio multimedia navigator in the "Vehicle" menu under "Electric drive" next to "Energy flow" if the automatic air conditioning has been activated. For this purpose, the climate control unit transmits the status and the electric drive control unit transmits appropriate information about energy consumption via the interior CAN to the audio gateway control unit, which transmits this information to the smart radio multimedia navigator via the telematics CAN.

AC component actuation function sequence 

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

Function sequence for actuation of blower motor 

Ventilation is achieved with the aid of the blower motor.

The blower motor is controlled via the blower regulator. The climate control unit actuates the blower regulator directly for this.

Function sequence for actuation of the 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 air ducting flaps are electrically adjusted via actuator motors:

G12097001Courtesy of MERCEDES-BENZ USA

Air outlets in the cockpit (shown on vehicle with engine 281) 

Function sequence for actuation of the electric refrigerant compressor and the electrical expansion valves (only vehicles with code l01 (Automatic air conditioning)) 

IMPORTANT The electrical expansion valve (vehicle interior) consists of the expansion valve on the evaporator itself and an electric solenoid valve, which is located in the high-pressure line upstream of the expansion valve (vehicle interior) and controls the flow of refrigerant to the expansion valve. The two subcomponents are connected via a high- pressure line. The electric solenoid valve of the electrical expansion valve (battery) is integrated into the housing of the expansion valve (battery) itself.

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

The output of the electric refrigerant compressor is controlled by the climate control unit. The climate control unit transmits the requests for actuating the electric refrigerant compressor via the interior CAN to the electric drive control unit. The electric drive control unit controls the electric refrigerant compressor via the electric drive LIN. The vehicle is equipped with an electrical expansion valve (vehicle interior) which is open when de-energized. If the electric refrigerant compressor is switched in, the pressurized refrigerant is injected into the evaporator in the air conditioner housing via the electrical expansion valve (vehicle interior) for cooling the vehicle interior.

As well as the variable of the climate control unit, with code V03 (Battery cooling system) the temperature of the high-voltage battery (G5), the high-voltage control unit box (N83), the charger for the high- voltage battery control unit (7 KW charger) (N83/5) or the charger for high-voltage battery control unit (22 KW charger) (N83/10) also has an influence on the control of the electric refrigerant compressor. By switching in the electric refrigerant compressor, the above-mentioned components can additionally be cooled via the low temperature coolant circuit. For this purpose, the electric drive control unit controls the electric refrigerant compressor via the electric drive LIN and transmits the requests to actuate the electrical expansion valve (battery) via the interior CAN to the climate control unit. The climate control unit actuates the electrical expansion valve (battery) (closed when de-energized) and the refrigerant is injected into the evaporator of the battery cooling system heat exchanger. The circulating coolant of the low temperature coolant circuit is thereby cooled.

If the climate control of the vehicle interior is switched off via the "A/C" button, the climate control unit actuates the solenoid valve of the electrical expansion valve (vehicle interior). The solenoid valve of the electrical expansion valve (vehicle interior) then blocks the flow of refrigerant to the expansion valve (vehicle interior). The refrigerant can then only be circulated in the refrigerant circuit of the high-voltage battery cooling. In this case, only the refrigerant circuit of the high-voltage battery cooling is cooled via the AAC, provided that this is required by the battery cooling system, otherwise the electric refrigerant compressor is switched off.

IMPORTANT Detailed information about the cooling of the low temperature coolant circuit, the refrigerant circuit of the high-voltage battery and high-voltage control unit box can be found in the separate "Thermal management, function" function description.

Function sequence for actuation of the fan motor 

The fan motor is used for cooling the coolant and refrigerant.

In vehicles with code I01 (Automatic air conditioning), the climate control unit calculates the specified fan speed depending on the refrigerant pressure, and transmits a request via the interior CAN to the electric drive control unit. The powertrain control unit then calculates the specified fan speed depending on the temperature of the liquid-cooled high-voltage components, the refrigerant of the low temperature coolant circuit, the request of the climate control unit and the refrigerant temperature and actuates the fan motor via the fan relay accordingly. In vehicles without code I01 (Automatic air conditioning), the fan motor is actuated independently of the status of the climate control.

Function sequence, heating mode 

Additional function requirements:

Heating of the vehicle interior does not take place via the coolant circuit in the smart e-drive, but with electricity only via the high voltage PTC heater. When this takes place, the air coming from the blower motor is heated up via the high voltage PTC heater and flows via the blend air flap and the air vents into the vehicle interior. The request for controlling the high voltage PTC heater is transmitted by the climate control unit via the interior CAN to the electric drive control unit. The powertrain control unit then regulates the high voltage PTC heater via the electric drive LIN. The high voltage PTC heater has output of 4 kW, which can be controlled from 0 to 100 %. In order to avoid overheating of the high voltage PTC heater, the system is equipped with a high voltage PTC heater temperature sensor.

The climate control unit controls the interior temperature that is set by the temperature control of the climate control operating unit. To do so, it actuates the blend air flap actuator motor directly and regulates the inflow temperature (blow air temperature) of the heating air with the aid of the vehicle interior humidity and temperature sensor.

Fresh air mode function sequence 

The fresh air/recirculated air flap is open and fresh air is delivered into the vehicle interior through the air conditioner housing.

Air recirculation mode function sequence 

Pressing the air recirculation mode button on the climate control operating unit closes the fresh air/recirculated air flap to prevent the air supply from outside. The air only circulates in the vehicle interior. This keeps unpleasant odors and pollutants away. The LED above the air recirculation mode button lights up during air recirculation mode. The climate control unit reads in the status of the air recirculation mode button via the climate control LIN and actuates the fresh air/recirculated air flap actuator motor directly. In vehicles with code I01 (Automatic air conditioning) and with an air quality sensor (country- dependent), the climate control unit also detects pollutants that penetrate into the vehicle via the ventilation system using the air quality sensor. If this is the case, the climate control unit automatically switches to air recirculation mode.

Function sequence for defroster function 

When the defroster button is pressed, all air flaps are closed with the exception of the fresh air/recirculated air flap. This is fully opened. The high-voltage PTC heater is switched in. The blend air flap is adjusted depending on the outside temperature - the maximum opening is limited so that the specified blowing air temperature of approx. T = 80 °C is not exceeded.

The climate control unit actuates the blower regulator, and this actuates the blower motor so that optimum defrost mode is provided depending on the exhaust air temperature.

In vehicles with code I01 (Automatic air conditioning) the electric refrigerant compressor is switched in order to ensure that the vent air is dried. The high-voltage PTC heater is also switched in. The air is dried and then heated up.

In vehicles without code I01 (Automatic air conditioning) only the high voltage PTC heater is switched in. The air is heated up.

Function sequence for automatic pre-entry climate control (only vehicles with code U14 (A/C package)) 

Additional function requirements:

Automatic activation when pre-heating is divided into the following subfunctions:

Pre-entry climate control at required point in time (time of day) via submenu in the instrument cluster 

Depending on the temperature of the vehicle interior, the pre-entry climate control at the required time of day must be distinguished into:

Pre-heat vehicle interior at required time of day 

In order to pre-climatize the vehicle, two times can be set at which the vehicle is pre-heated via the left multifunction steering wheel button group and the "Pre-entry climate control and charging" menu in the multifunction display of the instrument cluster. The point in time at which the pre-heating of the vehicle starts is calculated by the climate control unit depending on the interior temperature and the requirement. At normal outside temperatures, this starts approx. 10 to 20 min before the selected point in time. At cold outside temperatures, the pre-heating of the vehicle can start much earlier, but no more than 2 hours before the required point in time at which the vehicle should be pre-climatized. In order to do this, the instrument cluster transmits these time settings via the interior CAN (CAN B) to the center SAM control unit (N10/10) and also to the electric drive control unit. At the required switch-on time the center SAM control unit, which is the timer control master, then transmits the request to pre-heat the vehicle to the electric drive control unit. The electric drive control unit, which is the pre-entry climate control and energy management master, checks that the requirements are fulfilled, i.e. battery capacity status at least 45 %, and the charging capacity. The electric drive control unit receives this information via the electric drive CAN from the battery management system control unit. If the requirements are fulfilled, it transmits the request for pre-heating the vehicle in CAN message "PreHeatingActivation" via the interior CAN to the climate control unit. The climate control unit initiates the pre-climatization of the vehicle and therefore the activation of the fan. The fan is always operated at the 2nd stage. At cool outside temperatures (less than 18 °C) the high voltage PTC heater is switched in. The request for controlling the high voltage PTC heater is transmitted by the climate control unit via the interior CAN to the electric drive control unit. The powertrain control unit then regulates the high voltage PTC heater via the electric drive LIN. A temperature that has been preselected at the climate control unit has no influence on the pre-entry climate control function. The air distribution cannot be influenced by the pre-entry climate control. When the vehicle is switched off, the air distribution must be set to the required direction. If the selected pre-heating time is exceeded, the pre-heating is automatically shut off again after a certain time, unless the vehicle is unlocked or started. The pre-entry climate control of the vehicle is indicated in the multifunction display of the instrument cluster via an icon. In order to do this, the electric drive control unit transmits the CAN message "PreHeatingStateDisplay" via the interior CAN to the instrument cluster.

IMPORTANT During pre-heating, the climate control unit can also activate the seat heaters of the front seats. Detailed information can be found in the separate function description "Front seat heaters, function".

Pre-entry climate control (cooling) of vehicle interior at required time of day 

At an interior temperature of more than 21 °C the electric refrigerant compressor is switched on for pre-entry climate control instead of the electric high voltage PTC heater. The cooling output is selected so that an interior temperature of 21 °C is reached 5 minutes before the programmed departure. In order to do this, the climate control unit transmits the requests for actuating the electric refrigerant compressor via the interior CAN to the electric drive control unit. The electric drive control unit then controls the electric refrigerant compressor via the electric drive LIN. If the electric refrigerant compressor is switched in, the climate control unit actuates the electric expansion valve (vehicle interior) to cool the vehicle interior. The previous procedure corresponds to that of pre-heating, see "Pre-heating at required point in time".

Pre-entry climate control at required point in time (time of day) via vehicle home page (vehicles with "smart me" only) 

IMPORTANT The following abbreviation is used in the following text: Global System Mobile (GSM).

A menu for pre-entry climate control via a smartphone or PC can be called up via "smart me" and the vehicle homepage. In order to carry out pre-entry climate control, the telematics services communications module receives a GSM signal via the integrated GSM antenna in which two times of day can be set or activated in the telematics services communications module at which the vehicle is pre-climatized at a defined time. In order to do this, the telematics services communications module transmits these set times via the interior CAN to the center SAM control unit and also to the electric drive control unit. At the required switch-on time the center SAM control unit, which is the timer control master, then transmits the request to pre-climatize the vehicle to the electric drive control unit. After checking the existing requirements (sufficient battery capacity present), the electric drive control unit transmits the request to pre-climatize the vehicle in the CAN message "PreHeatingActivation" via the interior CAN to the climate control unit. The climate control unit then initiates pre-heating or pre- climatization of the vehicle depending on the interior temperature. The pre-heating is automatically shut off again approximately 10 min after the set time has been exceeded unless the vehicle is unlocked or started. The pre-entry climate control status of the vehicle is indicated in the multifunction display of the instrument cluster via an icon. The status is also indicated on the vehicle home page - in order to do this the electric drive control unit transmits the CAN message "PreHeatingStateDisplay" to the telematics services communications module. The telematics services communications module transmits the status via the integrated GSM antenna and a GSM signal to the vehicle home page, which can be called up via "smart me" with a smartphone or a PC.

IMPORTANT The pre-heating or pre-climatization (cooling) procedure of the vehicle interior in itself corresponds to the procedure "Pre-entry climate control at the required time (time of day) via submenu in the instrument cluster".

Function sequence for activating immediate pre-entry climate control via the vehicle homepage (vehicles with "smart me" only) 

Additional function requirements:

The pre-heating can also be switched on every now and then immediately by driver request via a smartphone or PC using "smart me" and the vehicle home page. In order to pre-heat the vehicle, the telematics services communications module receives a GSM signal via the integrated GSM antenna. It then transmits the request to pre-heat the vehicle via the interior CAN to the center SAM control unit. The center SAM control unit transmits the request to pre-heat the vehicle via the interior CAN to the electric drive control unit. After checking the existing requirements (sufficient battery capacity available), the electric drive control unit transmits this request via the interior CAN to the climate control unit. The climate control unit then initiates the preentry climate control of the vehicle. The temperature of the vehicle interior is controlled to a temperature of approx. 21 °C. After a certain pre-heating time (approx. 5 min) the pre-heating is shut off again. The pre-heating of the vehicle is displayed in the multifunction display of the instrument cluster. The pre-heating status is also indicated on the vehicle home page - in order to do this the electric drive control unit transmits the CAN message "PreHeatingStateDisplay" to the telematics services communications module.

IMPORTANT The pre-heating or pre-climatization (cooling) procedure of the vehicle interior in itself corresponds to the procedure "Pre-entry climate control at the required time (time of day) via submenu in the instrument cluster".

  Electrical function schematic for climate control input signals Vehicles without code I01 (Automatic air conditioning) PE83.40-P-2056-97BEB 
Vehicles with code I01 (Automatic air conditioning) PE83.40-P-2056-97BEA 
  Electrical function schematic for climate control output signals   PE83.40-P-2057-97BEA 
  Overview of system components for climate control   GF83.40-P-9994KJE 
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