Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Mercedes Benz >> 2021 >> G63 AMG >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Climate Control - 463 Chassis (1 Of 3) >> Basic Knowledge >> Climate Control Regulation, Function >> Climate Control Regulation, Function - GF83.40-P-2012GW

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

Model 463 (except 463.342) 

as of model year 2013 up to model year 2019 

Model 463.342 

G13659963Courtesy of MERCEDES-BENZ USA

Model 463 (except model 463.342), model 463.342 except code ZD4 (Vehicle for non-civilian use), model 463.342 with code ZD4 (Vehicle for non-civilian use), code F16 (Electric sliding roof with tilt function) and except code E11 (Stealth lights with convoy marking) 

G13659964Courtesy of MERCEDES-BENZ USA

Model 463.342 with code ZD4 (Vehicle for non-civilian use) and code E11 (Stealth lights with convoy marking) 

Function requirements, general 

IMPORTANT The electronic ignition lock control unit sends the status of circuit 15 via the interior CAN to the climate control, control and operating unit.

The CDI control unit (engine 642) or the ME-SFI [ME] control unit (engine 157, 273) sends the "Engine running" signal via the chassis CAN 1, electronic ignition lock control unit and interior CAN to the climate control, control and operating unit.

On vehicles with engine 176, the ME-SFI [ME] control unit sends the "Engine running" signal via the drive train CAN, powertrain control unit, chassis CAN 1, electronic ignition lock control unit and interior CAN to the climate control, control and operating unit.

Climate control, general 

The electronic temperature control and the air distribution in the vehicle interior are carried out depending on the selected settings at the climate control, control and operating unit and the variables recorded by various sensors (e.g. interior temperature, outside temperature, coolant temperature, vehicle speed). Determination of these variables is described below.

The climate control, control and operating unit is networked via the interior CAN and climate control LIN 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:

Recording and evaluation of variables 

The following variables are recorded and evaluated:

Outside temperature 

The outside temperature sensor measures the outside temperature.

The SAM control unit reads in the signal of the outside temperature sensor directly, calculates the outside temperature and transmits this via interior CAN to the climate control, control and operating unit. The climate control, control and operating unit needs this value in order 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 greater than 20 km/h. At speeds below 20 km/h and when the ignition is switched off and on, the last measured temperature value is used.

IMPORTANT The interior temperature is changed using the left blend air flap actuator motor for the driver and the right blend air flap actuator motor for the front passenger.

Interior temperature in head area 

Model 463 (except model 463.342), model 463.342 except code ZD4 (Vehicle for non-civilian use), model 463.342 with code ZD4 (Vehicle for non-civilian use) and code F16 (Electric sliding roof with tilt function) and except code E11 (Stealth lights with convoy marking): 

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 SAM control unit reads in the value of the interior temperature via roof LIN and transmits this via interior CAN to the climate control, control and operating unit.

Model 463.342 with code ZD4 (Vehicle for non-civilian use), code F16 (Electric sliding roof with tilt function) and code E11 (Stealth lights with convoy marking): 

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 stealth lights control unit reads in the interior temperature value via the stealth lights LIN and sends this via the roof LIN, SAM control unit and interior CAN to the climate control, control and operating unit.

Model 463.342 with code ZD4 (Vehicle for non-civilian use), code E11 (Stealth lights with convoy marking) and except code F16 (Electric sliding roof with tilt function): 

The interior temperature in the head area is recorded by the interior temperature sensor. The stealth lights control unit directly reads in the interior temperature sensor signals, calculates the interior temperature and sends this via the roof LIN, SAM control unit and interior CAN to the climate control, control and operating unit.

The integrated fan draws in air for the temperature measurement from the vehicle interior.

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 of the air outlet temperature sensors are directly read in by the climate control, control and operating unit. The climate control, control and operating unit regulates the air outlet temperature at the respective air outlets.

Windshield temperature and humidity (except model 463.342) 

The vehicle interior humidity and temperature sensor (except model 463.342) measures the relative air humidity and temperature directly at the inside of the windshield and uses this to determine the dew point temperature. The SAM control unit reads in the vehicle interior

humidity and temperature sensor signals via the roof LIN and sends them via the interior CAN to the climate control, control and operating unit.

Model 463.342 does not have a vehicle interior humidity and temperature sensor. A substitute value is stored in the climate control, control and operating unit for the dew point temperature.

If there is a risk of the windows fogging up, appropriate countermeasures are taken such as switching on the refrigerant compressor or starting the engine (with CODE MJ7 (ECO start/stop function)).

IMPORTANT When the windows start to fog up, the mirror heaters are also always switched on.

Coolant temperature 

The coolant temperature is recorded by the coolant temperature sensor. The CDI control unit or the ME-SFI [ME] control unit directly reads in the coolant temperature sensor signals and uses them to calculate the coolant temperature.

The CDI control unit (engine 642) or the ME-SFI [ME] control unit (engine 157, 273) then sends the coolant temperature via the chassis CAN 1, electronic ignition lock control unit and interior CAN to the climate control, control and operating unit.

On vehicles with engine 176, the ME-SFI [ME] control unit sends the coolant temperature via the drive train CAN, powertrain control unit, chassis CAN 1, electronic ignition lock control unit and interior CAN to the climate control, control and operating unit.

Temperature on evaporator 

To prevent the evaporator from icing up, the temperature there is recorded by the evaporator temperature sensor. The signals of the evaporator temperature sensor are read in directly by the automatic air conditioning control and operating unit.

If the evaporator temperature drops to approx. 2 °C, the refrigerant compressor is switched off.

Refrigerant pressure 

The refrigerant pressure is recorded by the refrigerant pressure sensor. The signals of the refrigerant pressure sensor are read in directly by the climate control, control and operating unit. The pressure is compared with a temperature-pressure curve stored in the climate control, control and operating unit. At a refrigerant pressure below 1.7 bar or over 30 bar, the refrigerant compressor is switched off or not switched on.

Solar radiation 

The sun sensor records the angle of incidence and the intensity of the solar radiation on the vehicle. The climate control, control and operating unit reads in the signals of the sun sensor directly and adapts the vehicle interior temperature and the blower speed accordingly.

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

Air quality 

The air quality sensor records the concentration of the following noxious gases:

The values are read in by the climate control, control and operating unit via climate control LIN. The climate control, control and operating unit implements the air recirculation to match the values read in.

Vehicle speed 

Vehicles except code E11 (Stealth lights with convoy marking)  :

The instrument cluster sends information on the vehicle speed via the interior CAN to the climate control, control and operating unit.

Vehicles with code E11 (Stealth lights with convoy marking): 

The instrument cluster sends information on the vehicle speed via the instrument cluster CAN, stealth lights control unit and interior CAN to the climate control, control and operating 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 recorded by the CDI control unit or by the ME-SFI [ME] control unit.

The CDI control unit (engine 642) or the ME-SFI [ME] control unit (engine 157, 273) sends the engine speed via the chassis CAN 1, electronic ignition lock control unit and interior CAN to the climate control, control and operating unit.

On vehicles with engine 176, the ME-SFI [ME] control unit sends the engine speed via the drive train CAN, powertrain control unit, chassis CAN 1, electronic ignition lock control unit and interior CAN to the climate control, control and operating unit.

The engine speed is used to regulate the refrigerant compressor, among other things.

Door status 

The status of each door is determined by the following control units and transmitted via the interior CAN to the climate control, control and operating unit:

The climate control, control and operating unit retains the current blower stage when the door is open in order to prevent unnecessary readjustment in the event of high temperature differences between the inside and outside air.

VCS [SBS] status (up to model year 2017, as of model year 2017 with code EU4 (COMAND Online)) 

If the VCS [SBS] is active, the blower motor output is restricted by the blower regulator. The COMAND controller unit transmits the status of VCS [SBS] via interior CAN to the climate control, control and operating unit.

Actuation of air conditioning components 

Actuation of the air conditioning components encompasses the following subfunctions:

Actuation of blower motor 

The through-ventilation of the vehicle interior is achieved with the support of the blower motor. The climate control, control and operating unit forwards the request over the climate control LIN to the blower regulator, which then actuates the blower motor.

As of 01.09.2015 the blower speed is reduced when the vehicle is at a standstill. This lowers disturbing blower noises at a standstill.

Actuation of air ducting flaps 

The air distribution in the vehicle interior is controlled by adjusting the air ducting flaps in the climate control housing.

The following air ducting flaps are adjusted:

IMPORTANT To prevent fogging of windows, the defroster flaps are closed 2 minutes after switching off circuit 15. After starting the engine, the defroster flaps remain in this fixed position for approx. 30 s. After that, all adjustments are possible again.

IMPORTANT At circuit 15 Off, the fresh air/recirculated air flap is adjusted by the fresh air/recirculated air flap actuator motor when one of the doors is opened to a partial recirculated air position. This achieves a significant reduction in the door closing forces. The function can be set with the diagnostic tester.

Air outlets in the cockpit and in the center console 

G13659965Courtesy of MERCEDES-BENZ USA

Actuation of refrigerant compressor 

The refrigerant compressor is responsible for induction and compression of the refrigerant. The refrigerant compressor is regulated continuously by the climate control, control and operating unit up to 100 % via the compressor control valve. The climate control, control and operating unit actuates the compressor control valve directly.

In addition, the climate control, control and operating unit sends the request to increase the idle speed via the interior CAN, electronic ignition lock control unit and chassis CAN 1 to the CDI control unit (engine 642) or the ME-SFI [ME] control unit (engine 157, 273).

On vehicles with engine 176, the climate control, control and operating unit sends the request to increase the idle speed via the interior CAN, electronic ignition lock control unit, chassis CAN 1, powertrain control unit and drive train CAN to the ME-SFI [ME] control unit.

The CDI control unit or ME-SFI [ME] control unit increases the idle speed in accordance with the additional load that occurs when the refrigerant compressor is switched on.

Actuation of fan motor 

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

The climate control, control and operating unit calculates the specified fan speed depending on the refrigerant pressure and sends the request via the interior CAN, electronic ignition lock control unit and chassis CAN 1 to the CDI control unit (engine 642) or the ME-SFI [ME] control unit (engine 157, 273).

On vehicles with engine 176, the climate control, control and operating unit sends the request via the interior CAN, electronic ignition lock control unit, chassis CAN 1, powertrain control unit and drive train CAN to the ME-SFI [ME] control unit.

The CDI control unit or the ME-SFI [ME] control unit calculates the target fan speed to match the engine temperature and actuates the fan motor accordingly.

Actuation of coolant circulation pump 

The coolant circulation pump is used for support when the engine is running or, when the residual heat mode is switched on, it pumps the coolant through the heater heat exchanger.

The climate control, control and operating unit actuates the coolant circulation pump directly.

Fresh air mode 

The fresh air/ram air/air recirculation flap is opened and fresh air is delivered into the vehicle interior through the air conditioner housing

Recirculated air mode 

Air recirculation mode encompasses the following subfunctions:

Air recirculation mode via the air recirculation mode button 

The fresh air/recirculated air flap is closed by pressing the air recirculation mode button on the climate control, control and operating unit in order to prevent air flow from 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.

Additional function requirements for pollutant-controlled air recirculation mode 

Pollutant-controlled air recirculation mode 

The air quality sensor transmits the pollutant values of the outside air via climate control LIN to the climate control, control and operating unit.

Starting from a certain pollutant concentration, the fresh 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 the requirement for pollutant-controlled air recirculation mode is met after the engine is started, fresh air is supplied for 30 s.

IMPORTANT The pollutant-controlled air recirculation mode is not shown via the LED of the air recirculation mode button.

Additional function requirements, defroster function 

Defrost function 

When the defroster button is pressed, all air flaps 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 climate control, control and operating unit regulates the blower regulator and this in turn regulates the blower motor via climate control LIN such that an optimum defrost mode is achieved depending on the outflow air temperature.

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.

Additional function requirements for evaporator drying process 

Evaporator drying 

To counteract any evaporator odor in the vehicle interior and any fogging of windows when starting the air conditioning, an evaporator drying process is conducted at the air conditioning system.

A timer is activated in the instrument cluster when the engine is switched off.

The CDI control unit (engine 642) or the ME-SFI [ME] control unit (engine 157, 273) sends the "Engine running" status via the chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the instrument cluster.

On vehicles with engine 176, the ME-SFI [ME] control unit sends the "Engine running" status via the drive train CAN, powertrain control unit, chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the instrument cluster.

After a waiting time of 1 h, the instrument cluster sends the request for the evaporator drying process via the interior CAN to the climate control, control and operating unit, which then starts the evaporator drying process. For this, the blower is actuated at the lowest stage for 30 minutes.

The climate control, control and operating unit transmits the blower request via the climate control LIN to the blower regulator. The blower regulator actuates the blower motor at the lowest blower stage. The air supply serves to reduce residual moisture in the evaporator.

Additional function requirements for maximum cooling output (with code ZU7 (Canada national version) or code ZU8 (USA national version)) 

Maximum cooling output (with code ZU7 (Canada national version) or code ZU8 (USA national version)) 

The blower output is raised to 100 % and the temperature set to minimum by pressing the "MAX COOL" button.

Residual heat utilization (except code ZU7 (Canada national version) and except code ZU8 (USA national version)) 

The function is switched off by pressing the "A/C REST" button on the climate control, control and operating unit. The climate control, control and operating unit actuates the coolant circulation pump directly. The coolant circulation pump delivers the still warm (residual heat) coolant through the heat exchanger. At the same time, the climate control, control and operating unit sends the ventilation request via climate control LIN to the blower regulator, which then actuates the blower motor at reduced power.

The air drawn in by the blower motor is routed along the heater heat exchanger and thus heated up. 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) 

To prevent the ingress of noxious gases into the vehicle interior in the event of an accident, the climate control, control and operating unit starts the following activities:

The supplemental restraint system control unit sends the crash signal via the chassis CAN 1, electronic ignition lock control unit and interior CAN to the climate control, control and operating unit.

  Electrical function schematic for climate control input signals   PE83.40-P-2056-97ZGA
  Electrical function schematic for climate control actuation   PE83.40-P-2057-97ZGA
  Overview of system components for climate control   GF83.40-P-9994GW 
scientia non olet · About Mike's Workshop Manuals