Climate Control -- Basic Knowledge -- 251 Chassis: Other Mercedes-Benz R-class W251 facelift

Automatic air conditioning refrigerant circuit, function - GF83.40-P-2005GM

MODEL 164.1 as of model year 09/YoM 08 model refinement package

MODEL 164.8, 251.0/1 as of model year 09/YoM 08

Scheme 210

Function requirements, general

1. Circuit 61
2. Air conditioning switched on

Automatic air conditioning refrigerant circuit, general

The interior air is cooled via the automatic air conditioning refrigerant circuit depending on the setting on the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning). The individual components are interconnected through lines and form a closed system.

The automatic air conditioning refrigerant circuit comprises the following subfunctions

1. Function sequence, high-pressure side
2. Function sequence, low-pressure side

Function sequence, high-pressure side

The refrigerant compressor driven by the engine takes in the gaseous refrigerant and compresses it. The refrigerant is heated up intensely in the process. The refrigerant is then pressed through the condenser at high pressure. The compression heat is extracted from the intensely heated refrigerant and diverted via the surface of the condenser (cooling fins). The refrigerant changes state from gaseous to liquid.

The refrigerant flows from the condenser to the fluid reservoir (drier). When the refrigerant flows through the fluid reservoir, it is cleansed of any chemical and mechanical contamination to protect the downstream components.

The cleansed refrigerant is forwarded to the expansion valve and the rear air conditioning refrigerant shutoff valve (with code (582) Rear air conditioning system). The expansion valve maintains the pressure at the high-pressure side.

Function sequence, low-pressure side

The expansion valve and the rear air conditioning refrigerant shutoff valve relieve the refrigerant pressure through volume enlargement. The state of the refrigerant changes from liquid to gaseous and the evaporative (heat) loss that is released is given off into the ambient air via the evaporator surface (cooling fins).

The cooled air is supplied to the vehicle interior via the blower motor (A32m1) and the rear air conditioning blower motor (M2/29) (with code (582) Rear air conditioning).

To prevent the particular evaporator from icing up, if the temperature drops below a specific value at the evaporator, the refrigerant compressor or the rear air conditioning refrigerant shutoff valve is switched off by the control and operating unit

Scheme 211

The temperature at the evaporator and the rear air conditioning evaporator is measured by the evaporator temperature sensor and the rear air conditioning evaporator temperature sensor.

Ventilation system function - GF83.10-P-2000RT

MODEL 251.1/0 with CODE (580) Automatic air conditioning up to Model Year 8

Function

The ventilation system prevents windows from misting up, provides oxygen to the occupants and ensures that uniform and pleasant temperatures in the interior are reached quickly.

In the normal mode, when the vehicle is stationary or in order to increase the air flow, the ventilation of the interior is achieved with assistance of the blower. Fresh air is drawn into the AC housing via the air inlet in the engine hood and via the fresh/recirculated air flap (fresh air position).

Scheme 212

Depending on preselection on the AAC [KLA] control and operating unit (N22), the air is directed through air ducts to the interior via air outlets. In the air recirculation mode, air is drawn out of the vehicle interior through the fresh air and air recirculation flaps (recirculated air position) and blown into the A/C housing.

In order to prevent the windows from fogging up, the defroster flaps as well as the air recirculation flap are closed and the footwell flaps opened completely 2 min after switching off the ignition. After starting the engine, the defroster flaps and footwell flaps remain in this position for 30 s. The air recirculation flap is immediately adjustable.

Ventilation system, function - GF83.10-P-2000RTK

MODEL 251.1/0 with CODE (581) Comfort automatic air conditioning with CODE (582) Rear air conditioner up to Model Year 8

MODEL 164.8 with CODE (581) Comfort automatic air conditioning with CODE (582) Rear air conditioner up to Model Year 8

Shown on model series 251

Function

The ventilation system prevents windows from misting up, provides oxygen to the occupants and ensures that uniform and pleasant temperatures in the interior are reached quickly.

During normal operation, when the vehicle is stationary or to increase the air volume, ventilation is carried out with the assistance of the front blower, the rear blower and, in the case of additional rear systems, with a well "rear blower".

Scheme 213

Fresh air is drawn into the air conditioner housing via the air inlet in the engine hood and via the fresh/recirculated air flap (fresh air position).

Depending on the preselection at the comfort AAC [KLA] control and operating unit (N22/7), the air is directed through air ducts and via air outlets into the vehicle interior. In the air recirculation mode, air is drawn out of the vehicle interior through the fresh air and air recirculation flaps (recirculated air position) and blown into the air conditioner housing.

In order to prevent the windows from fogging up, the defroster flaps and the air recirculation flap are closed and the footwell flaps opened completely 2 min after switching off the ignition. After starting the engine, the defroster flaps and footwell flaps remain in this position for 30 s. The air recirculation flap is immediately adjustable.

Automatic air conditioning (AAC), function - GF83.40-P-0001RT

MODEL 251.1/0 with CODE (580) Automatic air conditioning up to Model Year 8

Description

The automatic air conditioning (AAC) controls the equipment to achieve the interior temperature desired by the driver and passengers. The automatic air conditioning is available immediately after starting the engine. The system operates on the basis of the humidity and temperature. The ambient air is first cooled down by adding cooled air from the evaporator, even at low outdoor temperatures and then passes through the heat exchanger where it is heated up to the desired temperature.

The automatic air conditioning regulates the interior temperature and air distribution separately for the driver and passenger seats.

The system has the following sub-functions

Heating circuit

The coolant is heated up by the engine. When heat is required, heated coolant passes through the heating system heat exchanger where heat is transferred to the interior air. The coolant returns back to the coolant pump via the heater return.

Refrigerant circuit

The refrigerant compressor (A9) driven by the engine compresses the refrigerant vapor which is cooled down in the condenser. The refrigerant liquefies during cooling. The liquid refrigerant passes through the expansion valve into the evaporator, where it evaporates, cools down and removes the heat from the air that is flowing past, therefore cooling it down. The refrigerant compressor aspirates the refrigerant which has turned gaseous on account of the heat absorption and then compresses it yet again.

Ventilation

The ventilation system ventilates the interior of the vehicle. The air is drawn in by the blower motor (A32m1) and passes through the various air ducts to the air distribution flaps which distribute it in the vehicle interior.

Control

The electronic control for the automatic air conditioning is accomplished by various control units and temperature sensors connected with one another by the Control Area Network bus, class B (interior compartment) (CAN B), Control Area Network bus, class C (engine compartment) (CAN C) and Local Interconnect Network (LIN). The desired temperature is achieved or maintained at a constant level by cooling or heating the air.

OFF function

The air conditioning is switched off, the flap positions are maintained.

Engine residual heat utilization system

Utilization of the residual engine heat makes it possible to heat the vehicle even with the ignition "OFF". To do so the system utilizes the residual heat from the engine and guides it via the blower into the passenger compartment. The residual engine heat utilization feature is possible only when the ignition is "OFF".

Defrosting function

The defrosting function serves for keeping the windows free of fog and ice or quickly eliminating fogged windows by actuating the defroster outlet flap to the full open position and closing the footwell flaps. Function feedback is accomplished with a red LED.

A/C-OFF function

Compressor switched off, no cooling capacity. The transition cycle is accomplished to prevent the windows from fogging up. The defroster flaps are opened wider. Function feedback is accomplished with a red LED.

Recirculated air, function

Momentarily actuating the air recirculation button closes the main air flap to prevent air entering from outside. This ensures that the air circulates only in the interior compartment, keeping out unpleasant odors or pollution gases. The LED indicator comes on during operation. In the automatic mode, the control program can activate the recirculated air function.

Recirculated air convenience feature function

For easier operation, the windows and the tilting/sliding roof (SHD) (with code 414 power glass tilting/sliding roof) are closed automatically when the air recirculation switch (N22s2) is pressed for more than 1.5 s. When the air recirculation switch is actuated again, the windows and tilting/sliding roof (SR) return automatically to the previous positions.

The left vent window motor (M21/8) and right vent window motor (M21/9) are actuated via recirculated air convenience feature

1. AUTO button, function

When the Auto button is actuated, the AUTO mode is activated and the red LED in the AUTO button comes on. In automatic mode, the blower output and air distribution are controlled automatically, in addition to temperature control. Manually resetting the blower or the air distribution, terminates the AUTO mode. When the vehicle is restarted, the function last set is activated.

The blower level is higher on the US version than on the ECE version. In the event of maximum cooling output, "MAX COOL" is additionally shown in the USA version

Scheme 214

Convenience automatic air conditioning (C-AAC), function - GF83.40-P-0004RT

MODEL 251.1/0 with CODE (581) Comfort automatic air conditioning with CODE (582) Rear air conditioner up to Model Year 8

MODEL 164.8 with CODE (581) Comfort automatic air conditioning with CODE (582) Rear air conditioner up to Model Year 8

Function

The comfort automatic air conditioning (C-AAC) controls the interior temperature desired by the driver and the passengers. The comfort automatic air conditioning is operational immediately after the engine is started and produces the last stored temperature-controlled condition before the vehicle was locked. System operation is sensitive to humidity and temperature; even at low outside temperatures the ambient air is first cooled down by way of the evaporator's supply of cold air, and then routed through the heat exchanger and set to the desired passenger compartment temperature.

The C-AAC [K-KLA] controls the interior temperature separately for all 6 seats.

The comfort automatic air conditioning can be summarized with the subfunctions listed below

1. Heating circuit

The coolant is heated up by the engine. When heat is required, heated coolant passes through the heating system heat exchanger where heat is transferred to the interior air. The coolant returns back to the coolant pump via the heater return. The rear air conditioner is assisted by the rear AC additional circulation pump.

Refrigerant circuit

The refrigerant compressor (AC compressor) driven by the engine compresses the gaseous refrigerant, which is thereby heated up and routed to the condenser. The refrigerant's compression heat is then withdrawn on the surface of the condenser. The refrigerant liquefies when it cools down. Chemical and mechanical impurities are removed from the refrigerant in the downstream fluid reservoir. After cleaning, the liquid refrigerant is injected into the evaporator located in the fresh air flow. The refrigerant evaporates and cools down. Through this evaporation process heat is extracted from the fresh air flowing past from outside over the tube and fin system so that air cools down. The air humidity carried along is converted to condensed water, which is routed to the outside. The air is thus dried. The refrigerant compressor aspirates the refrigerant which has turned gaseous on account of the heat absorption and then compresses it yet again.

If required, the engine fan is switched on as well in the process. Cool air can be routed into the passenger compartment through the various air vents when the engine is running and the blower switched on.

The degree of cooling intensity is dependent upon the previously set in-car temperature and the blower output. A second evaporator is added to the refrigeration circuit in the form of the rear air conditioner.

1. Ventilation The ventilation system ventilates the interior of the vehicle. During normal operation, when the vehicle is stationary or in order to increase the air volume, ventilation is carried out with the assistance of the "front blower", the "booster blower" and also a "rear blower" belonging to the C-AAC. The air is led through various air ducts to the air distribution vents, through which it is distributed in the vehicle interior.
2. Control The comfort automatic air conditioning is controlled electronically via various control units and temperature sensors, which are interconnected via the Controller Area Network bus class B (interior) (CAN-B), the Controller Area Network Bus Class C (engine compartment) (CAN-C), and the local interconnect network (LIN). The desired temperature is achieved or maintained at a constant level by cooling or heating the air.
3. Engine residual heat utilization system The residual engine heat utilization makes it possible to heat or only ventilate the vehicle even when the engine is switched off. To do so the system utilizes the residual heat from the engine and guides it via the blower into the passenger compartment. The residual engine heat utilization feature is possible only when the ignition is "OFF".
4. Defrosting function The defrosting function serves for keeping the windows free of fog and ice or quickly eliminating fogged windows by actuating the defroster outlet flap to the full open position and closing the footwell flaps. Additionally, the refrigerant compressor is cut in, the fresh air flap is set to fully open and the coolant circulation pump (M13) and the rear AC additional circulation pump (M13/1) as well as the PTC heater booster (R22/3) (on diesel engines) are actuated.
5. AC-OFF function This function blocks the refrigerant compressor's cut-in. This takes place manually when the button on the comfort AAC [KLA] control and operating unit (N22/7) is pressed. The active AC OFF function is displayed by an LED.
6. Recirculated air, function When the air recirculation switch (N22s2) is actuated momentarily (t < 1.5 s), the fresh air supply is interrupted from outside by closing the fresh and air recirculation flap. This causes the air to circulate (closed windows and sliding roof assumed) in the interior only and keeps unpleasant odors or pollutants at bay. The function LED is illuminated during operation. The comfort automatic air conditioning is equipped with an automatic recirculation control.
7. Remote control for rear AC functions When the REAR button on the comfort AAC control and operating unit (N22/7) is pressed, the operating unit symbol appears in the front display. The blower setting is not visible. The rear temperatures can be set on the keyboard. The function is stopped automatically, if operation is not performed within approx. t = 5 s or the REAR button is pressed again. When the AUTO button or the REAR Button is pressed, the REAR operation can be stopped.
8. Emission-controlled recirculated air, function The emissions sensor (B31) transmits the pollutant values of the ambient air to the comfort AAC control and operating unit. The comfort AAC control and operating unit decides on the position of the air recirculation flap together with the dew point sensor (B11/12).

This function is not available with A/C OFF

OFF function

The air conditioning is switched off, the flap positions are maintained.

1. Recirculated air convenience feature function For easier operation, the windows and the tilting/sliding roof (SHD) (with power glass tilting/sliding roof, code 414) or the panoramic sliding roof (with panoramic sliding roof, code 413) are closed automatically when the air recirculation switch (N22/7s2) is pressed for more than 1.5 s. If the air recirculation switch is actuated again, the windows, the tilting/sliding roof (SHD) and the panoramic sliding roof automatically return to their previous positions. The left vent window motor (M21/8) and right vent window motor (M21/9) are actuated via recirculated air convenience feature.
2. AUTO button, function When the AUTO button is actuated, the AUTO mode is activated and the red LED in the AUTO button comes on. In automatic mode, the blower output and air distribution are controlled automatically, in addition to temperature control. Manually resetting the blower or the air distribution, terminates the AUTO mode. When the vehicle is restarted, the function last set is activated. The blower level is higher on the US version than on the ECE version. In the event of maximum cooling output, "MAX COOL" is additionally shown in the USA version.

Automatic air conditioning, function - GF83.40-P-0005GM

MODEL 164.1 as of model year 2009/YoM 08 model refinement package

MODEL 164.8, 251.0/1 as of model year 2009/YoM 08

Automatic air conditioning, general

Two different automatic air conditioning versions are installed

1. Standard automatic air conditioning with 2-zone temperature control (without code (581) Comfort automatic air conditioning)
2. Comfort automatic air conditioning with 3-zone temperature control (with code (581) Comfort automatic air conditioning) without and with rear air conditioning (model 164.8 and model 251 with code (582) Rear air conditioning)

The automatic air conditioning without code (581) Comfort automatic air conditioning is equipped with a separate temperature control for the driver side and the front passenger side.

Blower control takes place with 1 zone and can be operated manually or controlled automatically.

The automatic air conditioning with code (581) Comfort automatic air conditioning is equipped with separate temperature control for the driver side and the front passenger side and for the rear compartment.

Front and rear blower control takes place with 2 zones and can be operated manually or controlled automatically.

The cooling and heat output is increased in the rear area by the rear air conditioning (model 164.8 and model 251 with code (582) Rear air conditioning)

The regulation and control are carried out by the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or by the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning).

The automatic air conditioning comprises the following subfunctions

1. Heating circuit function sequence
2. Residual engine heat utilization function sequence
3. Function sequence for evaporator drying process (as of 1.9.08)

Further subfunctions are described in separate documents

1. Automatic air conditioning refrigerant circuit, function
2. Ventilation system, function
3. Regulation of Automatic air conditioning, function

Heating circuit function sequence

Driven by the coolant pump, the coolant circulates in the engine cooling circuit. In the process, it absorbs engine heat. The heated coolant is directed through the heater heat exchanger and the rear air conditioning heater heat exchanger (model 164.8 and model 251 with code (582) Rear air conditioning), which deliver the heat to the air blowing by.

Additionally, at low engine rpm, the coolant circulation pump (M13) is actuated to ensure that the flow volume needed to heat up the air blowing by is adequate.

The heater circulation pump is directly actuated by the control and operating unit.

Function requirements, residual engine heat utilization

1. Circuit 15C or circuit 15R ON

The circuit status of circuit 15 is provided by the EIS [EZS] control unit (N73) on the interior CAN (CAN-B)

Residual engine heat utilization function sequence

Pressing the REST button on the control and operating unit switches on the residual engine heat utilization function. The control and operating unit actuates the heater circulation pump directly. The coolant circulation pump delivers the coolant (residual heat) that is still warm through the heater heat exchanger.

The control and operating unit forwards the ventilation request to the blower regulator (A32n1) at the same time, whereupon the blower motor (A32m1) is actuated at slow speed by the blower regulator.

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

The function stops after approx. t = 30 min.

If the on-board electrical system voltage drops below a certain value, the function is automatically switched off by the on-board electrical system management system.

Function requirements, evaporator drying process (as of 1.9.08)

1. Air conditioning was active at least once during the ignition sequence
2. Evaporator temperature T > 3°C
3. Engine off (circuit 61 off)
4. Doors closed
5. Kilometer reading > 250 km

Function sequence for evaporator drying process (as of 1.9.08)

In order to counteract any evaporator odor in the interior and any fogging of the windows when starting the air conditioning system, an evaporator drying process is executed on the front air conditioning and the rear air conditioning (for model 164.8 and model 251 with code (582) Air conditioning system in rear).

At circuit 61 Off the timer in the instrument cluster (A1) is activated. The status of circuit 61 is placed on the engine compartment CAN (CAN C) by the CDI control unit (N3/9) (with diesel engine) or by the ME-SFI [ME] control unit (N3/10) (with gasoline engine).

After a waiting time of t = 1 h the instrument cluster sends the request for the evaporator drying process via the interior CAN to the control and operating unit, which then starts the evaporator drying process. To this end the blower is activated at the lowest setting for t = 30 min.

The control and operating unit sends the blower request over the climate control LIN (LIN B8) to the blower regulator (A32n1) and on model 164.8 and model 251 with code (582) Air conditioning system in the rear to the rear air conditioning blower regulator (N29/7). The blower regulator actuates the blower motor and the rear air conditioning blower regulator actuates the rear air conditioning blower motor (M2/29), at the lowest blower setting in each case.

Refrigerant circuit function - GF83.40-P-2001RT

MODEL 251.1/0 with CODE (580) Automatic air conditioning up to Model Year 8

Scheme 215

Function

The refrigerant compressor is driven by the engine and compresses the refrigerant vapor which is thereby heated up, and then passes into the condenser where it is cooled.

The refrigerant's compression heat is then withdrawn on the surface of the condenser. While cooling down, the refrigerant liquefies. When the refrigerant flows through the fluid reservoir it is cleansed of any chemical and mechanical impurities.

The liquid refrigerant passes through the expansion valve into the evaporator located in the fresh air flow. The refrigerant is then vaporized.

This evaporation process removes heat from the fresh air flowing through the system of tubes and fins from the outside, cooling it. The air humidity carried along is converted to condensed water, which is routed to the outside. The air dries out.

The refrigerant compressor aspirates the refrigerant which has turned gaseous on account of the heat absorption and then compresses it yet again.

The refrigerant pressure sensor monitors the pressure of the refrigerant.

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

MODEL 164.1 as of model year 2009/YoM 08 model refinement package

MODEL 164.8, 251.0/1 as of model year 2009/YoM 08

Function requirements, general

1. Circuit 15 On
2. Automatic air conditioning switched on
3. Circuit 61 ON (for cooling mode)
4. Refrigerant compressor (A9) switched on (for cooling mode)

The circuit status of circuit 15 is provided by the EIS [EZS] control unit (N73) on the interior CAN (CAN-B)

Automatic air conditioning regulation, general

The electronic regulation of the temperature and the air distribution in the interior compartment takes place depending on the settings selected on the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or on the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning) and the variables measured by various sensors (e.g. outside temperature, interior temperature, coolant temperature).

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 with the vehicle electronics system via the interior CAN, the climate control LIN (LIN B8) and direct lines. 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 regulation comprises the following subfunctions

1. Function sequence, recording of adjustments that are relevant for regulation
2. Function sequence, determining variables
3. AC component actuation function sequence

Function sequence, recording of adjustments that are relevant for regulation

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

1. Function sequence for automatic regulation
2. Function sequence with manual regulation
3. Function sequence of defroster function

Additional function requirements, automatic regulation

1. AUTO button pressed (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

1. Ambient temperature
2. Interior temperature
3. Coolant temperature
4. Temperature at the air outlets in the vehicle
5. Solar radiation on the vehicle
6. Vehicle speed
7. Temperature on evaporator
8. Temperature at rear air conditioning evaporator (with code (582) Rear air conditioning)
9. Refrigerant pressure
10. Engine speed
11. Pollutant concentration of the outside air (with code (581) Comfort automatic air conditioning)
12. Dew point temperature (with code (581) Comfort automatic air conditioning)
13. Door status and liftgate status
14. Window position
15. Tilting/sliding roof position (with code (414) Electric glass tilting/sliding roof) or panoramic sunroof position (model 251 with code (413) Panoramic glass sunroof with top sliding sunroof)
16. Vent window position (model 164.8 and model 251 with code (848) Electric side vent window)
17. Settings on the RCP [HBF] control unit (N72/2)
18. Status of voice control system (VCS [SBS]) (as of 1.7.09 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))

Additional function requirements, manual regulation

1. Air distribution and air volume changed manually (LED in AUTO button does not light up)

Function sequence with 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.

Additional function requirements, defroster function

1. Defroster button pressed (light emitting diode lights up)

Function sequence of defroster function

When the defroster button is pressed, all air flaps are closed with the exception of the defroster flaps and the fresh air/air recirculation flap. These are fully opened.

The defroster and side air vents are adjusted so that the maximum air flow is directed to the windshield and the front side windows. 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 through the left defroster flap actuator motor (M2/8) for the driver and 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 left and right defroster flaps actuator motor (M2/16).

Function sequence, determining variables

The function sequence for determining variables comprises the following subfunctions

1. Function sequence, determining the outside temperature
2. Function sequence, determining the interior temperature
3. Function sequence, determining the coolant temperature
4. Function sequence, determining the temperature at the air outlets in the vehicle
5. Function sequence, determining the vehicle speed
6. Function sequence, determining the solar radiation on the vehicle
7. Function sequence, determining the temperature on the evaporator and on the rear air conditioning evaporator (with code (582) Rear air conditioning)
8. Function sequence, determining the refrigerant pressure
9. Function sequence, determining the engine speed
10. Function sequence for determining the pollutant concentration of the outside air (with code (581) Comfort automatic air conditioning)
11. Function sequence for determining dew point temperature (with code (581) Comfort automatic air conditioning)
12. Function sequence, determining the door status and liftgate status
13. Function sequence, determining the window position
14. Function sequence, determining the tilting/sliding roof position (with code (414) Electric glass tilting/sliding roof) or the panoramic sunroof position (model 251 with code (413) Panoramic glass sunroof with top sliding sunroof)
15. Function sequence, determining the vent window position (model 164.8 and model 251 with code (848) Electric side vent window)
16. Function sequence, determining the settings on the RCP [HBF] control unit
17. Function sequence for determining the voice control system status (as of 1.7.09)

Function sequence, determining the outside temperature

The outside temperature indicator temperature sensor (B14) measures the outside temperature. The temperature value is read in directly by the control and operating unit.

Function sequence, determining the interior temperature

The interior temperature is measured by the in-car temperature sensor (N22b1) (without code (581) Comfort automatic air conditioning) or the In-car temperature sensor (N22/7b1) (with code (581) Comfort automatic air conditioning) in the control and operating unit.

The in-car temperature sensor is equipped with an aspirator blower which draws in air required for the temperature measurement out of the vehicle interior.

The aspirator blower ensures that the vehicle interior air is constantly circulated at the in-car temperature sensor and thus ensures a high degree of control accuracy.

By means of the in-car temperature sensor, a temperature control is achieved which is largely independent of the air flow conditions in the interior compartment.

Function sequence, determining the coolant temperature

The temperature of the coolant is registered by the coolant temperature sensor (B11/4). The temperature value is read by the CDI control unit (N3/9) (for diesel engines) or by the ME-SFI [ME] control unit (N3/10) (for gasoline engines) and transmitted to the central gateway control unit (N93) over the engine compartment CAN (CAN C). It transmits the value to the control and operating unit via interior CAN.

The value is used to control the blend air flaps, to regulate the PTC heater booster (R22/3) (for diesel engines) and to actuate the heater circulation pump (M13).

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

The temperature at the air outlets is recorded by the following sensors

1. Center rear interior temperature sensor (B10/7)
2. Left side air vent air outlet temperature sensor (B10/31)
3. Right side air vent air outlet temperature sensor (B10/32)
4. Left center outlet temperature sensor (B10/33)
5. Right center outlet temperature sensor (B10/34)
6. Left footwell air outlet temperature sensor (B10/35)
7. Right footwell air outlet temperature sensor (B10/36)
8. Rear headroom AC temperature sensor (B10/37) (with code (582) Rear air conditioning)

The control and operating unit regulates the outlet air temperature at the respective air outlets.

The temperature sensors are read in directly by the control and operating unit.

Function sequence, 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 for the internal calculation of the outside temperature, e.g. during operation while standing.

Function sequence, determining the solar radiation on the vehicle

The sun sensor (B32) (without code (581) Comfort automatic air conditioning) measures the intensity of the solar radiation acting on the vehicle using photo diodes.

The dual sun sensor (B32/3) (with code (581) Comfort automatic air conditioning) registers intensity and angle of incidence of the solar radiation on the vehicle. The dual sun sensor differentiates between left and right solar incidence, in other words it has two photodiodes. The measurement values are registered directly by the control and operating unit, and the interior temperature and the blower speed are adjusted accordingly.

Function sequence, determining the temperature on the evaporator and on the rear air conditioning evaporator

To prevent the evaporator and the rear air conditioning evaporator from icing up, their temperature is measured by the evaporator temperature sensor (B10/6) and the rear air conditioning evaporator temperature sensor (B10/11) (with code (582) Rear air conditioning) and read in directly by the control and operating unit. If the evaporator temperature drops to approx. T = 2°C, the refrigerant compressor or the rear air conditioning refrigerant shutoff valve (Y67) (with code (582) Rear air conditioning) is switched off.

Function sequence, determining the refrigerant pressure

The refrigerant pressure is measured by the refrigerant pressure sensor (B12) and compared to a temperature/pressure curve stored in the control and operating unit. At a certain value, the refrigerant compressor is switched off.

The refrigerant pressure sensor is read in directly by the control and operating unit.

Function sequence, determining the engine speed

The engine speed is registered by the CDI control unit or the ME-SFI [ME] control unit and transmitted to the central gateway control unit via engine compartment CAN. It transmits the value to the control and operating unit via interior CAN.

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

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).

The values are read in directly by the comfort AAC control and operating unit. The comfort AAC control and operating unit controls the automatic recirculation according to the read in values.

Function sequence for determining dew point temperature (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 comfort AAC 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 system and the heated outside mirror are activated by the comfort AAC control and operating unit.

Function sequence, determining the door status and liftgate status

The right front door rotary tumbler microswitch (M14/5s1), left front door rotary tumbler microswitch (M14/6s1), left rear door rotary tumbler microswitch (M14/8s1) and the right rear door rotary tumbler microswitch (M14/9s1) register the open or closed status of the relevant door.

The rear-end door locking unit (A72) registers the condition open or closed of the liftgate.

The door status and the liftgate status are read in by the rear SAM control unit (N10/8) and transmitted to the control and operating unit.

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

Function sequence, determining the window position

The left front window position is read in by the left front door control unit (N69/1), the right front window position by the right front door control unit (N69/2) and the particular rear window position by the front SAM control unit (N10) and transmitted to the control and operating unit.

Function sequence, determining the tilting/sliding roof position or the panoramic sunroof position (with code (414) Electric glass tilting/sliding roof) or the panoramic sunroof position (model 251 with code (413) Panoramic glass sunroof with top sliding sunroof)

The position of the tilting/sliding roof or the panoramic sunroof is read in by the overhead control panel control unit (N70) and transmitted to the control and operating unit.

Function sequence, determining the vent window position (Model 164.8 and model 251 with code (848) Electric side vent window)

The position of the vent windows is recorded by the rear SAM control unit on the basis of the signals from the left vent window motor (M21/8) and the right vent window motor (M21/9). The rear SAM control unit forwards the status to the control and operating unit via the interior CAN.

Function sequence, determining the settings on the RCP [HBF] control unit

The rear compartment climate control functions can be adjusted by the rear passengers via the RCP [HBF] control unit. The settings in the RCP [HBF] control unit are read in by the control and operating unit via interior CAN and processed.

AC component actuation function sequence

The AC component actuation function sequence comprises the following subfunctions

Function sequence for determining the voice control system status (as of 1.7.09)

The radio and navigation unit (A2/56) (with code (511) Audio 50 APS with DVD changer) or the COMAND operating, display and controller unit (A40/3) (with code (512) COMAND APS with DVD changer or with code (527) COMAND APS with single DVD drive (with navigation)) transmits the status of the VCS [SBS] to the control and operating unit via the interior CAN.

1. Function sequence, actuation of the refrigerant compressor
2. Function sequence, actuation of blower motor
3. Function sequence, actuation of the PTC heater booster
4. Function sequence, actuation of the air ducting flaps
5. Function sequence for actuation of engine and air conditioning electric suction fan with integrated control (M4/7)

Function sequence, actuation of the refrigerant compressor

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

The control and operating unit transmits the switch on requests directly to the compressor control valve.

Function sequence, actuation of blower motor

Ventilation is achieved with the aid of the blower motor. The control and operating unit transmits an actuation of 0 to 100% to the blower regulator via the climate control LIN. Depending on the control voltage, the blower regulator regulates the operating voltage for the blower motor from U = 0V up to U = 12V and thus the rotational speed of the blower motor from 0 up to 100%.

As of 1.7.09, the blower output is limited with an active VCS [SBS]

The actuation (operating voltage) of the blower motor is influenced by the following factors

1. Blower selector wheel setting ("MANUAL"/"AUTO")
2. "AC OFF" (On/Off)
3. Mode (heating/cooling)
4. Coolant temperature
5. Vehicle speed
6. Solar radiation
7. Fresh air/air recirculation flap position
8. Ambient temperature
9. Flap positions
10. Circuit 15 On (blower ON), circuit 50 On (starter running, blower off)
11. Window, tilting/sliding roof, panoramic sunroof position
12. Vent windows position
13. Air humidity (dew point) (with code (581) Comfort automatic air conditioning)
14. Pollutant concentration (with code (581) Comfort automatic air conditioning)
15. Residual engine heat utilization function
16. Variant coding

The blower output can be increased to match the outside temperature.

To keep the interior temperature constant and the windows clear at low temperatures, the blower output is increased by 15% at outside temperatures of T = -10°C to -15°C.

With code (581) Comfort automatic air conditioning without code (582) Rear air conditioning, the ventilation of the rear compartment is supported by the booster blower motor (M2/1). The actuation is carried out by the comfort AAC control and operating unit directly at the booster blower electronic blower regulator (N29/2). This directly actuates the booster blower motor.

With code (582) Rear air conditioner, ventilation of the rear compartment is assisted by the rear air conditioning system blower motor (M2/29). Actuation is carried out by the comfort AAC control and operating unit via the climate control LIN at the rear air conditioning system blower regulator (N29/7). This then actuates the rear air conditioning system blower motor directly.

Function sequence, actuation of the PTC heater booster

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

Air ducting flaps actuation function sequence

The control and operating unit actuates the following components for adjustment of the air ducting flaps via climate control LIN

Vehicles without code (581) Comfort automatic air conditioning

1. for fresh air/recirculated air control: Fresh air/air recirculation flap actuator motor (M2/5)
2. for temperature control: Left blend air flap actuator motor (M2/6) Right blend air flap actuator motor (M2/7)
3. for ventilation control: Rear shutoff flap actuator motor (M2/12) Left and right footwell flaps actuator motor (M2/15) Left and right defroster flaps actuator motor Rear air distribution flap actuator motor (M2/21) Center vent flap actuator motor (M2/22)

Vehicles with code (581) Comfort automatic air conditioning

1. for fresh air/recirculated air control: Fresh air/air recirculation flap actuator motor
2. for temperature control: Left blend air flap actuator motor Right blend air flap actuator motor
3. for ventilation control: Left defroster flap actuator motor Right defroster flap actuator motor Left footwell flap actuator motor (M2/10) Right footwell flap actuator motor (M2/11) Rear shutoff flap actuator motor Center vent flap actuator motor Left center air flap actuator motor (M16/23) Right center air flap actuator motor (M16/24)

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

The electric suction fan serves to cool the coolant and refrigerant. The control and operating unit calculates the specified fan speed depending on the refrigerant pressure and transmits the request to the central gateway control unit via interior CAN.

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

Electrical function schematic for automatic air conditioning, input signals Model 164 PE83.40-P-2052-97MAA Model 251 PE83.40-P-2052-97RAA Electrical function schematic for automatic air conditioning, actuation Model 164 PE83.40-P-2053-97MAA Model 251 PE83.40-P-2053-97RAA Instrument cluster, component description A1 GF54.30-P-6000GM Radio/navigation unit, component description A2/56 With code (511) Audio 50 APS with DVD changer GF82.61-P-4111GQA Component description for COMAND operating, display and controller unit A40/3 With code (527) COMAND APS with single DVD drive (with navigation) without code (498) Japan version or code (512) COMAND APS with DVD changer GF82.85-P-3134GQ With code (527) COMAND APS with single DVD drive (with navigation) with code (498) Japan version GF82.85-P-3134GQJ Component description for CDI control unit N3/9 On engine 629.9 in model 164 GF07.16-P-6000OAG On engine 642.8 with code (U42) BlueTec diesel exhaust gas cleaning (SCR) with AdBlue®/DEF and with code (494) USA version GF07.16-P-6000OGU On engine 642.9 GF07.16-P-6000OHG ME-SFI [ME] control unit, component description N3/10 With engine 156 in model 164 GF07.61-P-6000MAG On engine 272 GF07.61-P-6000MIG With engine 273 GF07.61-P-6000MLG Component description for front SAM control unit N10 GF54.21-P-7010GM Component description for rear SAM control unit N10/8 GF54.21-P-7030GM Component description for automatic air conditioning control and operating unit N22 Without code (581) Comfort automatic air conditioning GF83.40-P-3000GM Comfort automatic air conditioning control and operating unit, component description N22/7 With code (581) Comfort automatic air conditioning GF83.40-P-3010GM Left front door control unit, component description N69/1 GF72.29-P-4141GM Right front door control unit, component description N69/2 GF72.29-P-4142GM Overhead control panel control unit, component description N70 GF82.20-P-5216GM Rear control panel control unit, component description N72/2 Without code (581) Comfort automatic air conditioning GF83.40-P-3020GMA with code (581) Comfort automatic air conditioning GF83.40-P-3020GMB Component description for EIS [EZS] control unit N73 GF80.57-P-6003GM Central gateway control unit, component description N93 GF54.21-P-4170GM

MODEL 164.1 as of model year 09/YoM 08 model refinement package

MODEL 164.8, 251.0/1 as of model year 09/YoM 08

Scheme 216

Function requirements, general

1. Circuit 61
2. Air conditioning switched on

Automatic air conditioning refrigerant circuit, general

The interior air is cooled via the automatic air conditioning refrigerant circuit depending on the setting on the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning). The individual components are interconnected through lines and form a closed system.

The automatic air conditioning refrigerant circuit comprises the following subfunctions

1. Function sequence, high-pressure side
2. Function sequence, low-pressure side

Function sequence, high-pressure side

The refrigerant compressor driven by the engine takes in the gaseous refrigerant and compresses it. The refrigerant is heated up intensely in the process. The refrigerant is then pressed through the condenser at high pressure. The compression heat is extracted from the intensely heated refrigerant and diverted via the surface of the condenser (cooling fins). The refrigerant changes state from gaseous to liquid.

The refrigerant flows from the condenser to the fluid reservoir (drier). When the refrigerant flows through the fluid reservoir, it is cleansed of any chemical and mechanical contamination to protect the downstream components.

The cleansed refrigerant is forwarded to the expansion valve and the rear air conditioning refrigerant shutoff valve (with code (582) Rear air conditioning system). The expansion valve maintains the pressure at the high-pressure side.

Function sequence, low-pressure side

The expansion valve and the rear air conditioning refrigerant shutoff valve relieve the refrigerant pressure through volume enlargement. The state of the refrigerant changes from liquid to gaseous and the evaporative (heat) loss that is released is given off into the ambient air via the evaporator surface (cooling fins).

The cooled air is supplied to the vehicle interior via the blower motor (A32m1) and the rear air conditioning blower motor (M2/29) (with code (582) Rear air conditioning).

To prevent the particular evaporator from icing up, if the temperature drops below a specific value at the evaporator, the refrigerant compressor or the rear air conditioning refrigerant shutoff valve is switched off by the control and operating unit. The temperature at the evaporator and the rear air conditioning evaporator is measured by the evaporator temperature sensor and the rear air conditioning evaporator temperature sensor

Survey of automatic air conditioning (AAC), system components - GF83.40-P-9992RT

MODEL 251.1/0 with CODE (580) Automatic air conditioning up to Model Year 8

Stationary heater (STH), function - GF83.70-P-0006GM

MODEL 164.1 with CODE (228) Stationary heater as of model year 2009/YoM 08 model refinement package

MODEL 164.8,251.0/1 with CODE (228) Stationary heater as of model year 2009/YoM 08

General function requirements

1. Sufficient remaining quantity of fuel in tank

Stationary heater (STH), general

Before starting the trip the STH ensures

1. the interior compartment is preheated
2. the windows are free of ice and condensation
3. the engine is preheated

The use of the stationary heater reduces

1. the accident hazard by providing clear visibility before starting out on a trip
2. the mechanical wear to the automotive engine associated with a cold start
3. fuel consumption and at the same time it also helps to protect the environment by reducing the pollutants in the exhaust when starting up a preheated engine

The stationary heater also contains the stationary ventilation function. This provides for the following at high ambient temperatures and a high interior temperature due to intense solar radiation

1. the interior is ventilated
2. stored heat is reduced

It is not possible to cool the vehicle interior to below the outside temperature

Heating or ventilation mode can be triggered in the following ways

1. immediately via the STH switch (N72/1s30) or STH radio remote control transmitter (A8/3)
2. preprogrammed via the left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111)

The main component is the STH heater unit (A6). The STH heater unit comprises all components necessary for generating and exchanging heat.

The STH heater unit is directly connected to the heating and cooling circuit of the vehicle engine. The auxiliary heater metering pump (M46/1) provides the fuel supply for the STH heater unit.

The STH is comprised of the following subfunctions

1. Function sequence, teach-in of STH transmitter
2. Function sequence, trigger immediate heating mode with STH transmitter
3. Function sequence, trigger immediate heating mode with STH switch
4. Function sequence, programming of preselection time
5. Function sequence, trigger heater preselect mode
6. Function sequence, decide to heat or ventilate
7. Function sequence, heating mode
8. Function sequence, ventilation mode
9. Function sequence, component test
10. Function sequence, STH shutoff

Function sequence, teach-in of STH transmitter

Before initial startup the STH radio remote control receiver (A6/1) must undergo a "teach-in" of the STH transmitters allocated to it. For this purpose, the STH switch must be pressed for approx. t = 20 s until the red LED in the STH switch flashes on and off.

The actuation of the STH switch is read in by the upper control panel control unit (N72/1) and transmitted to the STH control unit (A6n1) via the interior CAN (CAN B). After the STH switch has been actuated for approx. t = 20 s, the STH control unit transmits feedback to the upper control panel control unit and the red LED in the STH switch is triggered to flash.

As soon as the red LED starts to flash, the STH switch must be released to open the teach-in period window. The request to open the teach-in period window is read in by the upper control panel control unit and transmitted to the STH control unit via interior CAN. This transmits the request to the STH receiver and the teach-in period window is opened for max. t = 5 s.

The "OFF" button on the STH transmitter must be pressed during this period. The signal is transmitted by the STH transmitter via radio to the roof antenna module (A2/93). From there, the signal is transmitted directly to the STH receiver or, with code (386) Mobile phone comfort telephony, directly to the telephone/cell phone/STH radio remote control antenna splitter (A2/53) and from there on to the STH receiver. The STH receiver saves the first, valid transmission signal it receives as the signal from the STH transmitter allocated to it. Following this, it then closes the teach-in period window and it has to be opened again to teach in another STH transmitter.

The STH receiver can store up to three STH transmitters. If an additional STH transmitter undergoes teach-in, then the STH transmitter that underwent teach-in first is deleted.

The teach-in period window can also be opened using the diagnostic tester. The various opening times can only be configured using the diagnostic tester, similarly the number of STH transmitters that have undergone teach-in are read out

The radio signal path is bidirectional i.e. if a radio signal from the STH transmitter does not reach the STH receiver, this is indicated on the STH transmitter

The range of the stationary heater transmitter is s = 300 m. External influences can reduce the range, for example

1. radio interference
2. solid obstacles (e.g. enclosed premises)
3. unfavorable position to the vehicle

Function sequence, trigger immediate heating mode with STH transmitter

If the "ON" button on the stationary heater transmitter is pressed, the switch-on signal is transmitted by radio. This is detected by the roof antenna module and transmitted directly to the STH receiver or, with code (386) Mobile phone comfort telephony, directly to the antenna splitter and then relayed to the STH receiver. The STH receiver transmits the switch-on signal to the STH control unit, which transmits the query "Ventilate or heat" via interior CAN to the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or to the comfort AAC control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning).

The radio signal path is bidirectional i.e. if a radio signal does not reach the STH receiver, this is displayed on the STH transmitter

The range of the stationary heater transmitter is s = 300 m. External influences can reduce the range, for example

1. radio interference
2. solid obstacles (e.g. enclosed premises)
3. unfavorable position to the vehicle

Function sequence, trigger immediate heating mode with STH switch

Triggering the immediate heating mode function sequence with the STH switch consists of the following subfunctions

1. Function sequence, trigger immediate heating mode with circuit 15R Off
2. Function sequence, trigger immediate heating mode with circuit 15R On

Additional function requirements for triggering immediate heating mode with circuit 15R Off

1. Circuit 15R OFF

Terminal status c. 15 is provided by the EIS control unit (N73) to the interior CAN

Function sequence, trigger immediate heating mode with circuit 15R Off

When the STH switch is actuated, the switch-on signal is read in by the upper control panel control unit and transmitted via interior CAN to the STH control unit, which transmits the query "Ventilate or heat" to the control and operating unit via interior CAN.

Additional function requirements for triggering immediate heating mode with circuit 15R On

1. Circuit 15R ON

Function sequence, trigger immediate heating mode with circuit 15R On

When the STH switch is actuated for t > 2 s, the switch-on signal is transmitted by the upper control panel control unit to the STH control unit via interior CAN. The STH control unit transmits the request "Ventilate or heat" via the interior CAN to the control and operating unit and also sends a request to the instrument cluster (A1) via the interior CAN to open the preselection time menu.

The preselection times are shown via the multifunction display (A1p13) of the instrument cluster.

When the STH switch is actuated for t < 2 s, only the preselection time menu is called up in the instrument cluster, the STH is not switched on

Additional function requirements for programming preselection time

1. Circuit 15R ON

The preselection time corresponds to the desired starting time for the stationary heater (up to 30.6.09) or the desired shutdown time (as of 1.7.09)

Function sequence, programming of preselection time

The preselection time menu is called up in the instrument cluster via the multifunction steering wheel button groups. The request is transmitted via the steering LIN (LIN E1) to the steering column tube module (N80) and from there via the engine compartment CAN (CAN C) to the instrument cluster.

The preselection time is displayed on the multifunction display of the instrument cluster.

The preselection time menu can also be called up via the STH switch. When the STH switch is actuated for t < 2 s, the preselection time menu is called up but the STH is not switched on. At the same time the status of the STH switch is read in by the upper control panel control unit and transmitted to the STH control unit via the interior CAN. The STH control unit transmits a request to the instrument cluster to open the preselection time menu via interior CAN. The preselection time is then set using the multifunction steering wheel button groups and can be activated by selecting the corresponding preselection time.

The instrument cluster stores a maximum of three preselection times.

When the STH switch is actuated for t > 2 s, the preselection time menu in the instrument cluster is called up and the query "Ventilate or heat" is transmitted to the control and operating unit

Additional function requirements for triggering heater preselect mode

1. Circuit 15C OFF
2. Preselection time activated

Function sequence, trigger heater preselect mode

On vehicles up to 30.6.09

At the determined start time, the instrument cluster transmits the switch-on command to the STH control unit via interior CAN, which transmits the query "Ventilate or heat" to the control and operating unit via interior CAN. The STH control unit also transmits a signal to the upper control panel control unit via interior CAN and the yellow LED in the STH switch lights up. The yellow LED goes out after the STH is switched on.

The preselection time corresponds to the desired STH starting time

The activation via a current preselection time is suppressed if heating mode has been switched on manually in the meantime

For vehicles as of 1.7.09

After a preselection time has been activated, the instrument cluster calculates the time remaining until the preselection time based on the current time and activated preselection time. The STH control unit also transmits a signal to the UCP [OBF] control unit via interior CAN and the yellow LED in the STH switch lights up. The yellow LED goes out after the STH is switched on.

One hour before the entered preselection time, the instrument cluster transmits a query to the control and operating unit via interior CAN to determine the period of heating/ventilation that is actually required. Based on the current outside and interior temperature measurements, the control and operating unit determines the optimal duration of heating/ventilation.

The outside temperature is recorded by the outside temperature indicator temperature sensor (B14) and read directly by the control and operating unit. The interior temperature is measured by the in-car temperature sensor (N22b1) (without code (581) Comfort automatic air conditioning) or the in-car temperature sensor (N22/7b1) (with code (581) Comfort automatic air conditioning) in the control and operating unit. The duration of heating/ventilation is transmitted to the instrument cluster via interior CAN. The instrument cluster determines the switch-on time based on the preselection time and the required period of heating/ventilation.

At the determined switch-on time, the instrument cluster transmits the switch-on command to the STH control unit via interior CAN, which transmits the query "Ventilate or heat" to the control and operating unit via interior CAN.

preselection time corresponds to the desired departure time

The activation via a current preselection time is suppressed if heating mode has been switched on manually in the meantime

Function sequence, decide to heat or ventilate

The STH control unit transmits the query "Ventilate or heat" to the control and operating unit via interior CAN.

Based on the current outside and interior temperature measurements, the control and operating unit determines the optimal duration of heating/ventilation.

The outside temperature is recorded by the outside temperature indicator temperature sensor and read in directly by the control and operating unit.

The interior temperature is measured by the in-car temperature sensor in the AAC control and operating unit.

It then decides whether to "Ventilate or heat" depending on the values determined and the last setting of the control and operating unit.

The red LED in the STH switch lights up while the decision is being made. The LED is actuated from the STH control unit via the upper control panel control unit via interior CAN. After t = 2 s, the STH control unit is informed of the decision to "Ventilate or heat" via interior CAN and either heating or ventilation mode is switched on. The decision is indicated visually by the LED in the STH switch. The red LED indicates stationary heating, and the blue LED stationary ventilation. The LED is actuated as described above. The STH control unit also reports the corresponding status back to the STH transmitter.

The following messages may be displayed on the STH transmitter

1. "FAIL": No wireless connection or heater operation not possible (note corresponding symbol)
2. "ON": STH activated
3. "OFF": STH deactivated

When the STH is switched on, a query on the status of all components involved in the heating mode is conducted and a self-test is performed if required. The heating mode is not started in the event of a relevant fault. The stationary ventilation function however is always performed, irrespective of the result

Function sequence, heating mode

After the decision to "Heat" is made, the STH control unit starts the heating mode. The combustion air blower (A6m2) is actuated and operates close to its highest speed. The glow pin of the flame monitor glow pin unit (A6r4) is switched on. The preglow time of approx. t = 30 s starts.

After the preglow time, the combustion air blower is switched off briefly and the auxiliary heater metering pump starts to pump fuel. The combustion air blower starts again and, like the auxiliary heater metering pump, increases its speed and output to full load within the next approx. t = 60 s.

The fuel and the combustion air form the fuel/air mixture in the combustor housing. Once the increase in the flow of combustion air and fuel delivery has been completed, the glow pin of the flame monitor glow pin unit is switched off, and the safety period begins for approx. t = 45 s to check the flame.

After the end of the safety period and during heating mode, the flame monitor glow pin unit reports the following statuses in its function as flame monitor

1. "hot" = sufficient combustion, heater operation continues.
2. "cold" = no flame, flame-out or insufficient flame formation, the auxiliary heater metering pump is switched off. On vehicles with gasoline engine, startup is repeated once. If there is still no flame formation, fuel supply is stopped by switching off the auxiliary heater metering pump and fault shutoff with combustion air blower run-on takes place.

The STH switchover valve (Y16) is closed at coolant temperatures T < 60°C (small coolant circuit). As of T = 60°C, it is pulse actuated by the STH control unit and the large coolant circuit is then also heated. The coolant circulation pump (M13) ensures that the temperature-controlled coolant is circulated in the coolant circuit. It is actuated directly by the control and operating unit.

If the temperature is sufficient, the control and operating unit actuates the blower regulator (A32n1) via the climate control LIN (LIN B8). This actuates the blower motor (A32m1).

The heater operation is controlled automatically depending on the coolant temperature. Possible operating states

1. Full load operation
2. Partial load operation
3. Control interval

The stationary heater primarily heats up the vehicle interior. Heating of the engine coolant is a secondary function. If the engine is started during heating operation, the engine first heats up itself, then starts to heat the interior once the coolant temperature in the engine (large circuit) has exceeded the temperature of the heat exchanger (small circuit)

Depending on the interior temperature, a switchover from stationary heating to stationary ventilation and vice versa can be made

Function sequence, ventilation mode

After the decision is made to "Ventilate", only the ventilation in the vehicle is switched on. The control and operating unit actuates the blower regulator via the climate control LIN, which then actuates the blower motor.

Depending on the interior temperature, a switchover from stationary ventilation to stationary heating and vice versa can be made

Function sequence, component test

When the STH is switched on, a check is made to determine whether a component fault was stored during the previous heater operation (component status) or whether the STH heater unit is disabled due to fault or overheating.

If a relevant fault is found to be stored in the STH control unit, no start attempt is made and a component test is performed instead. If no faults are detected any more, the component status is set to OK for the next switch-on attempt.

The following components are monitored for open circuit, short circuit and proper operation during startup and during heater operation

1. Temperature sensor (A6b1)
2. Thermal fuse (A6f1)
3. Circulation pump (A6m1)
4. Fuel preheating system (A6r5) (with diesel engine)
5. Combustion air blower
6. Glow pin unit flame monitor
7. Auxiliary heater metering pump
8. STH switchover valve

If a fault is detected, the heater operation startup process or heater operation is only aborted if the faulty component is essential for operation

This is not the case for the STH switchover valve, a fault with the STH switchover valve does not cause heater operation to be terminated. The STH switchover valve is thus not taken into account when assessing the component status.

The tank content is also checked during STH startup. The tank status is stored every time circuit 15 is switched off so that the information is available immediately upon startup. Heater operation is only started if there is enough fuel left in the tank.

Compliance with the tank reserve signal can be disabled using the diagnostic tester

Function sequence, STH shutoff

The STH shut-off function sequence comprises the following subfunctions

1. Function sequence, terminate heating mode
2. Function sequence, terminate ventilation mode
3. Function sequence, shutoff due to overheating
4. Function sequence, safety shutoff due to crash

Function sequence, terminate heating mode

Heating mode is automatically terminated by the STH control unit or it can be manually aborted early using the STH transmitter or STH switch. With the basic setting, the maximum heating time is t = 50 min. This can be changed in t = 10 min steps between t = 10 min and t = 60 min using the diagnostic tester.

The combustion is terminated by switching the auxiliary heater metering pump off. The run-on time of the combustion air blower starts.

The run-on time and speed of the combustion air blower depend on the operating condition (full-load operation, partial load operation or control pause) from which the STH heater unit was switched off.

If the engine is started during heating mode, expiration of the heating time is ignored and the system continues to heat until the coolant temperature of the engine (large circuit) exceeds the temperature of the heat exchanger (small circuit) by T = 5°C

Function sequence, terminate ventilation mode

Ventilation mode is automatically terminated by the STH control unit or it can be manually aborted early using the STH transmitter or STH switch. With the basic setting, the maximum ventilation time is limited to t = 50 min, as is the heating time.

This can be changed in t = 10 min steps between t = 10 min and t = 60 min using the diagnostic tester.

A shortening factor can also be set using the diagnostic tester. The following shortening factors can be set

1. Factor 1: ventilation time = 3/4 heating time
2. Factor 2: ventilation time = 1/2 heating time
3. Factor 3: ventilation time = 1/4 heating time

Function sequence, shutoff due to overheating

If the temperature of T = 125°C is exceeded in the STH heater unit, the thermal fuse detects overheating and triggers the heater unit fault run-on process for approx. t = 120 s followed by fault interlock. Operation after shutoff via the thermal fuse resumes

1. via the diagnostic tester or
2. via temporary interruption of the power supply (e.g. fuse removal). To do this, the STH switch must first be operated for at least t = 5 s up to a maximum of t = 15 s. After releasing the STH switch, the fuse must be removed within t = 30 s to achieve a reset of the fault interlock.

Function sequence, safety shutoff due to crash

The restraint systems control unit (N2/7) transmits the crash signal via engine compartment CAN to the central gateway control unit (N93). The central gateway control unit forwards the signal via interior CAN to the STH control unit, which then switches off the STH heater unit permanently.

The shutoff process can only be reset using the diagnostic tester.

Stationary heater (STH), location of components Model 164 GF83.70-P-0006-01GM Model 251 GF83.70-P-0006-01GV Electrical function schematic, teach-in of stationary heater radio remote control transmitter Model 164 PE83.70-P-2052-97MAA Model 251 PE83.70-P-2052-97RAA Electrical function schematic, trigger immediate heating mode Model 164 PE83.70-P-2053-97MAA Model 251 PE83.70-P-2053-97RAA Electrical function schematic, programming of preselection time Model 164 PE83.70-P-2055-97MAA Model 251 PE83.70-P-2055-97RAA Electrical function schematic, trigger heater preselect mode Model 164 PE83.70-P-2054-97MAA Model 251 PE83.70-P-2054-97RAA Stationary heater (STH) block diagram GF83.70-P-0006-04GM Instrument cluster, component description A1 GF54.30-P-6000GM STH control unit, component description A6n1 GF83.70-P-4200GM Restraint systems control unit, component description N2/7 GF91.60-P-4048GM Component description for automatic air conditioning control and operating unit N22 Without code (581) Comfort automatic air conditioning GF83.40-P-3000GM Comfort automatic air conditioning control and operating unit, component description N22/7 With code (581) Comfort automatic air conditioning GF83.40-P-3010GM Upper control panel control unit, component description N72/1 GF54.21-P-6040GM Component description for EIS [EZS] control unit N73 GF80.57-P-6003GM Component description for steering column tube module control unit N80 GF54.21-P-6051GM Central gateway control unit, component description N93 GF54.21-P-4170GM

Stationary heater (STH), function - GF83.70-P-0006GZ

MODEL 164,251 up to Model Year 8 Nur ECE-Fahrzeuge

General information

Prior to starting a journey during the cold season the stationary heater (STH) ensures that

1. the interior is preheated
2. the windows are free of ice and condensation
3. the engine is preheated

The use of the stationary heater reduces

1. the accident hazard by providing clear visibility before starting out on a trip
2. the mechanical wear to the automotive engine associated with a cold start
3. fuel consumption and at the same time it also helps to protect the environment by reducing the pollutants in the exhaust when starting up a preheated engine

The stationary heater also contains the stationary ventilation function.

This provides for the following at high ambient temperatures and a high interior temperature due to intense solar radiation

1. the interior is ventilated
2. stored heat is reduced

It is not possible to reduce the temperature below the outside temperature

The main component is the STH heater unit (A6). The heater unit comprises all components necessary for generating and exchanging heat.

The heater unit is connected directly to the heater and coolant circuits for the automotive engine and utilizes them, together with its own circulation pump (M13), to transmit heat.

The auxiliary heater metering pump (M46/1) provides the fuel supply for the heater unit.

To enable the interior to be heated up faster, the heater unit regulates the flow of coolant to match temperature between the small and large coolant circuit by way of the STH switchover valve (Y16).

Possible activation modes

The heater mode or stationary ventilation can

1. be preprogrammed via the instrument cluster (A1) or
2. switched on using the STH radio remote control transmitter (A8/3) or
3. with the STH switch (N72/1 s30) be triggered.

In the instrument cluster up to three preselect times can be stored, of which only one can be activated. The preselection times are shown via the multifunction display (A1p13) in the instrument cluster.

Terminate heater mode or stationary ventilation

The functions are automatically terminated by the stationary heater itself or they can be manually canceled in advance using the stationary heater transmitter or the STH switch.

Safety shutoff in the event of crash

The restraint systems control unit (N2/7) sends the crash signal via the Controller Area Network bus class C (engine compartment) (CAN-C) to the central gateway control unit (N93), which issues the signal on the Controller Area Network bus class B (interior) (CAN-B). The front SAM control unit (N10) receives the crash signal and switches the heater unit permanently off. The safety shutoff can only be reset via diagnosis.

Shutoff via thermal fuse

In the event of a temperature control fault or a fault due to overheating, e.g. as a result of a lack of water, the thermal fuse switches the heater unit permanently off when a temperature of 125°C is exceeded.

Operation after shutoff via the thermal fuse resumes

1. via diagnosis or
2. by breaking the contact of the power supply for a short period of time (e.g. removing the fuse). To do this, the STH switch must first be operated for at least 5 s up to a maximum of 15 s. After releasing the STH switch, the fuse must be removed within 30 s to achieve a reset of the thermal fuse.

Engine start during stationary heater operation

The stationary heater primarily heats up the vehicle interior. Heating of the engine coolant is secondary. If the engine is started during stationary heater operation, the engine initially heats itself and only starts to heat the interior once the coolant temperature in the vehicle's engine (large circuit) exceeds the temperature of the heat exchanger (small circuit).

Teach-in of the STH transmitter

Before initial startup, it is necessary to teach in the transmitters allocated to the STH radio remote control receiver (A6/1). For this purpose, the STH switch must be pressed for approx. 20 s until the red indicator lamp in the STH switch flashes on and off.

Release the STH switch as soon as the red indicator lamp is flashing. A time window of 5 s is now open that can be used to teach in. The "OFF" button on the transmitter key must be pressed during this period.

The STH radio remote control receiver remembers the first incoming valid signal and the time window closes.

The procedure must be repeated to teach in another transmitter key. The STH radio remote control receiver stores a maximum of 3 transmitters. If a fourth transmitter is added, the transmitter that was first taught in is deleted

The time window to teach in the stationary heater transmitter and the number of stationary heater transmitters that have been taught in can be opened or read out via the diagnosis

Switchover between stationary heater and stationary ventilation

The AAC [KLA] control and operating unit (N22) (with code (580) Automatic air conditioning) or the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning) can correct its heating or ventilation decision as and when needed. During a heating period, switching between ventilation and heating may occur, depending on temperature behavior.

Activate heater immediately with radio remote control, function - GF83.70-P-3057GZ

MODEL 164,251 up to Model Year 8 Nur ECE-Fahrzeuge

Scheme 217

Function requirements

1. Circuit 30
2. Sufficient remaining quantity of fuel in tank

Function

When the "ON" button on the stationary heater transmitter is pressed, the request is sent per radio to the roof antenna module. This forwards the signal to the stationary heater receiver via the telephone antenna splitter. After the received signal is checked, it is transmitted to the STH control unit. This then initiates the "Ventilate or heat" query at the control and operating unit via CAN-B. Depending on the equipment, the control and operating unit then determines the current interior temperature via the

1. In-car temperature sensor (N22b1) (with code (580) Automatic air conditioning)
2. In-car temperature sensor (N22/7b1) (with code (581) Comfort automatic air conditioning)

Depending on the determined interior and outside temperatures, the control and operating unit then decides between heat or ventilate and sends the decision to the stationary heater control unit.

During operation, the control and operating unit can switch over between heating and ventilating any number of times to obtain the desired target temperature irrespective of outside temperature and solar radiation. Visual confirmation is provided by an indicator lamp in the STH switch

1. Blue: Vehicle is ventilated
2. Red: Vehicle is heated

HEATING

The metering pump is actuated to supply fuel and the heater unit starts heater operation.

To enable the interior to be heated up faster, the heater unit regulates the flow of coolant between the small and large coolant circuit to match temperature by way of the stationary heater switchover valve.

The coolant circulation pump ensures that the temperature-controlled coolant is circulated in the coolant circuit.

With a sufficient temperature, the control and operating unit actuates the blower motor via the blower regulator.

VENTILATION

During stationary ventilation only the blower is actuated in the vehicle.

The control and operating unit actuates the blower motor via the blower regulator.

Feedback (up to 31.5.07)

The indicator lamp in the stationary heater transmitter may display the following

1. Indicator lamp (green or red) is continuously on for 2 s: Correct wireless connection to the vehicle has been established.
2. Indicator lamp (green or red) flashes for 2 s: Correct wireless connection to the vehicle has not been established.
3. Indicator lamp (orange) is continuously on for 2 s before the green or red signal (regardless whether it flashes or is continuously on): The battery in the stationary heater transmitter is weak but transmission is still possible.
4. Indicator lamp (orange) flashes for 5 s: The battery in the stationary heater transmitter is too weak for transmission.

When switched on, the signal on the stationary heater transmitter is confirmed with a green signal, when switched off by a red signal

Feedback (as of 1.6.07)

The stationary heater control unit reports the operating condition back to the stationary heater transmitter.

Possible displays

1. "FAIL": No wireless connection or heater operation not possible (note corresponding symbol)
2. "ON": Stationary heater activated
3. "OFF": Stationary heater deactivated

Operating time for heater and ventilation

In the basic setting, the maximum heating time is 50 min. It is possible to change it to between 10 and 60 min in 10 min. increments via diagnosis.

The maximum ventilation time is limited to a maximum of 50 min. in the basic setting, as is the heating time, unless a shortening factor was set via diagnosis.

The following shortening factors can be set

1. Factor 1: ventilation time = 3/4 heating time
2. Factor 2: ventilation time =1/2 heating time
3. Factor 3: ventilation time =1/4 heating time

The range of the stationary heater transmitter is approx. 300 m, but it can also be reduced through external influences

Activate preprogrammed heater, function - GF83.70-P-3058GZ

MODEL 164,251 up to Model Year 8

Nur ECE-Fahrzeuge

Scheme 218

The starting time of the stationary heater is set in the instrument cluster via the stationary heater menu. The starting time is set with the left or right multifunction steering wheel button group and can be activated by selecting the corresponding starting time.

Once the starting time is activated, visual confirmation is provided via a continuously on yellow indicator lamp in the STH switch.

The instrument cluster stores a maximum of 3 starting times.

Function requirement

1. Circuit 15R ON
2. Starting time in the instrument cluster activated
3. Fuel gauge is not in reserve

Function

When the set starting time has been reached, the instrument cluster sends the switch-on signal to the STH control unit via CAN-B.

Thereupon, the STH control unit transmits, via CAN-B, a query to the AAC [KLA] control and operating unit to check whether heating or ventilating is required.

The AAC [KLA] control and operating unit determines, depending on the target temperature last set on the operating unit, whether heating or ventilating is required and returns the corresponding message to the STH control unit.

During operation, the AAC [KLA] control and operating unit can switch over between heating and ventilating any number of times to obtain the desired target temperature irrespective of outside temperature and solar radiation. Visual confirmation is provided by an indicator lamp in the STH switch

1. Blue: vehicle is ventilated
2. Red: vehicle is heated

Heating mode

The STH control unit switches the auxiliary heater metering pump as well as the STH switchover valve on and actuates the blower motor. The coolant circulation pump is actuated by the AAC [KLA] control and operating unit.

To obtain the set target temperature in the interior as quickly as possible, the STH control unit regulates the coolant flow between the small and the large coolant circuit heated by the STH heater unit (A6) dependent on the temperature via the STH switchover valve. The coolant circulation pump ensures that the temperature-controlled coolant is circulated in the coolant circuit.

Ventilation

The STH control unit only actuates the blower motor.

Operating time for heater and ventilation

In the basic setting, the maximum heating time is 50 min. It is possible to change it via diagnosis in 10 min increments between 10 and 60 min.

The maximum ventilation time is limited to a maximum of 50 min in the basic setting, as is the heating time, unless a shortening factor was set via diagnosis.

The following shortening factors can be set

1. Factor 1: ventilation time = 1/3 heating time
2. Factor 2: ventilation time = 1/2 heating time
3. Factor 3: ventilation time = 1/4 heating time

Activate heater with stationary heater switch, function - GF83.70-P-3066GZ

MODEL 164,251 up to Model Year 8

Nur ECE-Fahrzeuge

Scheme 219

Function requirements

1. Circuit 30
2. Fuel gauge is not in reserve

Function

After actuation of the STH switch, the upper control panel control unit sends the signal for switching on the stationary heater to the STH control unit via CAN-B.

Thereupon, the STH control unit transmits a query to the AAC [KLA] control and operating unit via CAN-B to check whether heating or ventilating is required.

The AAC [KLA] control and operating unit determines, depending on the target temperature last set on the operating unit, whether heating or ventilating is required and returns the corresponding message to the STH control unit.

During operation, the AAC [KLA] control and operating unit can switch over between heating and ventilating any number of times to obtain the desired target temperature irrespective of outside temperature and solar radiation. Visual confirmation is provided by an indicator lamp in the STH switch

1. Blue: vehicle is ventilated
2. Red: vehicle is heated

Heating mode

The STH control unit switches the auxiliary heater metering pump as well as the STH switchover valve on and actuates the blower motor. The coolant circulation pump is actuated by the AAC [KLA] control and operating unit.

To obtain the set target temperature in the interior as quickly as possible, the STH control unit regulates the coolant flow between the small and the large coolant circuit heated by the STH heater unit (A6) dependent on the temperature via the STH switchover valve.

The coolant circulation pump ensures that the temperature-controlled coolant is circulated in the coolant circuit.

Ventilation

The STH control unit only actuates the blower motor.

Operating time for heater and ventilation

In the basic setting, the maximum heating time is 50 min. It is possible to change it via diagnosis in 10 min increments between 10 and 60 min.

The maximum ventilation time is limited to a maximum of 50 min in the basic setting, as is the heating time, unless a shortening factor was set via diagnosis.

The following shortening factors can be set

1. Factor 1: ventilation time = 1/3 heating time
2. Factor 2: ventilation time = 1/2 heating time
3. Factor 3: ventilation time = 1/4 heating time

Residual engine heat utilization function - GF83.75-P-2000RT

MODEL 251.1/0 up to Model Year 8

Function

The residual engine heat utilization feature makes it possible to continue to heat or simply ventilate the vehicle with c. 15 Off or c. 15C. For this purpose, the system utilizes the residual engine heat by pumping the still hot coolant through the heating system heat exchanger with the coolant circulation pump (M13) and blowing the heated air into the vehicle interior with the blower motor (A32m1).

The coolant circulation pump is actuated by the AAC operating and control unit (N22) or comfort AAC operating and control unit (N22/7).