Part 2
- Radiator fan
Besides the engine cooling, the radiator fan is also needed for cooling the condensers. The radiator fan is actuated by the DME/DDE.
Signal path:
IHKR or IHKA control unit -> K-CAN -> Junction box electronics (serves as data interface) -> PT-CAN -> DME/DDE -> Radiator fan
- Condenser with integrated dehumidifier flask (IHKR, IHKA only)
Refrigerant is converted from gas into liquid in the condenser. In the integrated drier flask, which is installed downstream of the condenser, any water that may be present in the refrigerant circuit is collected. The drier element can be exchanged.
- Expansion valve (IHKR, IHKA only)
The expansion valve controls the injection quantity into the evaporator. Only as much liquid refrigerant enters the evaporator as the evaporator is able to completely evaporate. Drops of liquid that have not been evaporated would cause damage in the A/C compressor.
The expansion valve is fitted directly to the engine compartment bulkhead.
Additional components:
- Microfilter
Fresh air for interior ventilation is fed through a microfilter.
> E81, E82, E87, E90, E91, E92, E93: IHR, IHKR
When a filter replacement is needed, this will be indicated by the Condition Based Service (CBS) (until 03/2007).
from 03/2007: Filter replacement: see Service Booklet
> E70: IHKA
Filter replacement: see Service Booklet
- Microfilter with activated charcoal
On the IHKA, a microfilter with activated carbon is fitted. The activated-charcoal filter helps to provide additional purification of the incoming fresh air from gaseous pollutant emissions.
> E81, E82, E87, E90, E91, E92, E93: IHKA
When a filter replacement is needed, this will be indicated by the Condition Based Service (CBS) (until 03/2007).
from 03/2007: Filter replacement: see Service Booklet
> E70: IHKA
Filter replacement: see Service Booklet
- Stratification control and rear stratification control
> E70 IHKA High and E90, E91, E92, E93 IHKA
The selected potentiometer setting is transposed into the flap position of the specific flap motor (front and rear stratifying flap motor and rear ventilation flap motor).
> E70 IHKA High with automatic rear air conditioning
Due to the separate settings for the left and right sides in the rear, there are 2 rear stratification controls and 2 ventilation flap motors in the rear.
- LIN bus
A data line supplies all component on the LIN bus with the necessary control information. This data line also carries the status reports of the components back to the IHR/IHKR/IHKA control unit. The control unit controls the following components via the LIN bus:
- Electric auxiliary heater
- Flap motors
The following control units contribute to the operation of the IHR/IHKR/IHKA:
- SZM: Centre console switch cluster
The SZM is connected to the IHR/IHKR/IHKA control unit via a 14-pin connector.
The IHR/IHKR/IHKA control unit serves as the interface between the SZM and the K-CAN.
The IHR/IHKR/IHKA control unit assumes the following tasks for the SZM:
- Reading off settings made by pressing buttons
- Actuating LEDs for function lighting
- Dimming LEDs for function and search lighting
- Forwarding relevant CAN messages
- JBE: Junction box electronics
The JBE is the data interface (= gateway) between the K-CAN and the PT-CAN. (K-CAN = body CAN; PT-CAN = powertrain CAN.)
The JBE receives input signals from some of the sensors and control units (e.g. AUC sensor, DME/DDE control unit, IHR/IHKR/IHKA control unit).
The junction box consists of the JBE and the power distributor. Amongst other things, the power distributor supplies power to the heated rear window. The JBE controls the heated rear window.
- M-ASK or CCC or CHAMP: Multi-audio system controller or Car Communication Computer or multimedia platform
The controller signals for selecting the menu are processed in the M-ASK or CCC or CHAMP (multimedia platform: CHAMP; Central Head Unit and Multimedia Platform).
To actuate the CID (Central Information Display), the red-green-blue signals from the graphics processor are converted into digital signals.
- CAS: Car access system
The CAS comprises the remote control functions, amongst other things.
The CAS assigns a personal ID code to every remote control. The CAS transfers the personal ID code to the IHKA control unit via the K-CAN.
Key-based settings (Key Memory) are stored in the IHKA control unit.
When the vehicle is unlocked, the remote control unit used is recognised. The settings stored for this unit are called up and executed.
In the run-down period, the current settings are stored for the remote control unit in use at that time.
- DME or DDE: Digital engine electronics or digital diesel electronics
The DME/DDE actuates the radiator fan.
On vehicles with diesel engine, the DDE provides the electric auxiliary heater with information about the maximum electrical power available (with a pulse-width modulated signal).
The maximum electrical power available depends on the load on the alternator.
- Control and display functions via controller and Central Information Display (IHKA only)
The following control and display functions are selected and activated with the controller in the CID (Central Information Display):
- Air distribution setting
The defrost flaps, ventilation flaps and footwell flaps can be individually set in the air distribution submenu.
- Automatic mode
The intensity of the IHKA can be set in the automatic mode submenu. In other words, the automatic influence of the climate conditions outside the vehicle on the air volume and the opening angle of the flaps can be set to one of three different settings (low, medium, high).
> E70 with IHKA High
The settings can be selected and activated at the IHKA control panel.
- Automatic rear air conditioning
> E70 with IHKA High
The automatic rear air conditioning can be activated or deactivated in the "Automatic program" submenu.
The function "Use driver's settings" can be selected to adopt the (driver's) settings from the IHKA control panel for the FKA control panel.
System functions
The IHR/IHKR/IHKA comprises the following functions:
- Temperature control
- Evaporator control (IHKR/IHKA only)
- Air distribution setting
- Airflow control
- Sunlight compensation (solar sensor)
- MAX cooling (IHKA only)
- Residual heat (IHKA only)
- Defrost function (IHKA only)
- AUTO function (IHKA only)
- Heated rear window
- OFF
- Air recirculation mode
- Automatic air-recirculation control (IHKA only)
- Program for preventing condensation on the window surfaces (IHKA only)
- Central kinematics actuation (IHR, IHKR only)
- Convertible program (E93 only)
- Independent heater (option 536)
- Automatic rear air conditioning (option 4NB, E70 only)
- Additional heating/ventilation for 3rd row of seats (option 4NC, E70 only)
- Seat heating and active seat ventilation (E70 only)
- Steering wheel heating
- Electric steering column adjustment
Temperature control
- E81, E82, E87, E90, E91, E92, E93: Heating and air-conditioning system controlled on the air side
The temperature for the best possible interior climate is regulated with a mixer flap in the heater/air conditioner.
The air-mass flow is fed through the evaporator (IHKR, IHKA only). As this happens, the air-mass flow is cooled and dried (providing the air-conditioning system is switched on). The mixer flap then feeds the air-mass flow completely or in part over the heating system heat exchanger and the electric auxiliary heater (depending on the desired temperature value set at the IHR/IHKR/IHKA control panel). The air flows are subsequently mixed again. The air-mass flow is then fed through the ventilation flaps and into the vehicle interior.
On the IHKA, the air ducts for the driver and front-passenger are separate. Due to the separate settings for the left and right sides for the driver and front passenger there are 2 mixing flaps.
- IHR, IHKR
Temperature control is based on the nominal value set and a calculated actual value (The nominal value is set at the temperature selector wheel on the IHR/IHKR control panel. The actual value is calculated from the temperatures measured by the ventilation temperature sensor and the footwell temperature sensor.)
With the IHR, temperature control below the ambient temperature is not possible.
- IHKA
Control is based on the nominal values set and the calculated actual value (The nominal values are set using 2 temperature selector wheels on the IHKA control panel (separate settings for left and right sides). The actual value is calculated from the temperatures measured by the interior temperature sensor and the footwell temperature sensor).
The lead parameter is calculated from the comparison between the actual value for the interior temperature and the corrected nominal value (calculated from temperature request and ambient temperature). Compared to the set specification, the interior temperature is raised in the cold so that a comfortable level is achieved even at negative temperatures, despite the temperature setting being unchanged. The ambient temperature is transmitted to the IHKA control unit via the body CAN (body Controller Area Network).
- E70: Heating and air-conditioning system controlled on the water side
Within the heating/air-conditioning systems, the air-mass flow is first fed through the evaporator. As this happens, the air-mass flow is cooled and dried (providing the air-conditioning system is switched on). The air-mass flow is then fed over the heating system heat exchanger and the electric auxiliary heater,where it is heated up to the required nominal value (depending on the desired temperature value set at the IHKA control panel). The air-mass flow is then fed through the ventilation flaps and into the vehicle interior.
The IHKA High has separate air ducts for the driver and front passenger. The separate settings for the driver and front-passenger side means that the heating system heat exchanger also has separate settings for the left and right sides.
- IHKA Basic
The temperature in the heating system heat exchanger is controlled with the help of the heating system heat exchanger sensor and a pulsed water valve in the heater circuit. The water valve is actuated with a pulse-modulated signal (PWM signal) by the IHKA control unit. A map for the heating system heat exchanger determines the opening times for the water valve, depending on the engine speed.
Regulation is based on the nominal value set by the vehicle occupants at the temperature selector wheel and the calculated actual value. (nominal values are set via a temperature selector wheel on the IHKA control panel.
The actual value is calculated from the temperatures measured by the interior temperature sensor and the heating system heat exchanger sensor).
The lead parameter is calculated from the comparison between the actual value for the interior temperature and the corrected nominal value (calculated from temperature request and ambient temperature). Compared to the set specification, the interior temperature is raised in the cold so that a comfortable level is achieved even at negative temperatures, despite the temperature setting being unchanged.
The ambient temperature is transmitted to the IHKA control unit via the body CAN (body Controller Area Network).
- IHKA High
The separate temperature setting for the drivers side and the front-passenger side affects:
- Heating system heat exchanger with left/right separation
- 2 heating system heat exchanger sensors
- 2 ventilation temperature sensors
- Dual water valve
Evaporator control (IHKR, IHKA only)
The evaporator temperature is regulated by means of the evaporator temperature sensor and the expansion valve. The evaporator temperature is set to the predefined specification of 2 �C. Lower temperatures are not possible due to the risk of icing.
If the "variable evaporator control" function has been encoded, the nominal evaporator temperature is calculated between 2 and 7°C. The specification depends on the ambient temperature, the ventilation temperature and the refrigerant pressure. A variable evaporator control reduces dehumidification. This reduces the risk of mucous membranes drying out.
Air distribution setting
For the best possible operation of the air distribution, it is important for the manually adjustable air vents to be open.
- IHR, IHKR
Air distribution selection is only possible manually with the air-distribution control wheel.
- IHKA
Occupants have the possibility of allowing the air distribution to be decided by the automatic program (AUTO button).
Alternatively, individual, personal settings are possible through manual selection (defrost, ventilation, footwell).
If the relevant equipment is fitted to the vehicle, it is also possible to make a fine adjustment via the CID (Central Information Display) in the submenu Air distribution.
Compared to manual selection, fine adjustment offers the additional possibility of further individualisation of the air distribution.
> E70: IHKA Basic
With the IHKA Basic, the air distribution can only be set manually with the controller.
The menu provides the following settings:
- 4 different presettings and
one individually configured setting
The vehicle occupants can effect individual air distribution/stratification of hot and cold air inside the vehicle at the same temperature setting.
> E70: IHKA High
In addition, air distribution can also be set at the IHKA control panel.
The menu provides the following settings:
- Driver's side:
4 different presettings and
one individually configured setting
- Passenger side:
3 different presettings and
one individually configured setting
Settings for ventilation temperature (temperature stratification) can also be made in this menu.
With the IHKA High, separate stratification can be set for the left and right sides in the front. Stratification is also possible in the rear.
> E70: IHKA High with automatic rear air conditioning
With the IHKA High with automatic rear air conditioning, stratification can be set separately for the left and right sides in the rear.
Airflow control
The airflow control is dependent on the following settings and control actions:
- Manual blower setting
- Automatic blower and flap setting (IHKA only)
The automatic blower and flap functions are activated when the AUTO button is pressed.
- Dynamic pressure compensation
The air volume at the air inlet grilles increases disproportionately with increasing road speed. This effect is compensated for by the opening angle of the fresh-air flap being reduced as speed increases (dynamic pressure compensation).
The opening angle is regulated according to a defined map.
- Blower control
If necessary, the power management system will assign priority levels to reduce the blower output (via K-CAN).
- Effect of terminal 50
When the engine is being started (terminal 50 ON), the electric auxiliary heater and blower are switched OFF to reduce the load on the car battery.
Sunlight compensation (solar sensor)
> E70 IHKA High and E81, E82, E87, E90, E91, E92, E93 IHKA
The following functions are modified when automatic mode is activated (depending on the intensity of sunlight):
- Blower output is increased or reduced
- Desired temperature value is increased or reduced
> E70 High
The influence on IHKA regulation by the solar sensor is assigned separately to the driver's side and to the front-passenger side.
> E81, E82, E87, E90, E91, E92, E93 IHKA
How the solar sensor affects the IHKA regulation on the driver's side and on the front-passenger side is not programmed separately.
MAX cooling (IHKA only)
The MAX button makes it possible for the user to select maximum cooling with just one press of a button at the IHKA controls.
When the MAX button is pressed, all functions, including the defrost function, are deactivated. The air-conditioning function is activated (if it was not already activated) and defined settings are selected (e.g. temperature control is deactivated, ventilation flaps are fully opened).
Residual heat (IHKA only)
The residual-heat function allows the waste heat from the engine to be used to heat up the vehicle interior when the engine is not running (e.g. during a stop at a level crossing). The residual-heat function is only possible for a certain run-down period (15 minutes from terminal 15 OFF). The auxiliary water pump is activated to circulate the water.
Switch-on conditions:
- Terminal 15 OFF
and
- Run-down period active (up to 15 minutes after terminal 15 OFF)
and
- REST button* in IHKA controls ON
and
- Ambient temperature below 25°C
and
- Engine temperature at some point above 60°C
and
- On-board supply voltage over 11.4 volts
Condition for switching off:
- Terminal 15 ON
or
- Residual heat ON (15 minutes) expired
or
- REST button* in IHKA control panel OFF
or
- OFF condition activated with residual heat active (terminal R)
or
- Prompt from power management to switch off auxiliary consumers
or
- On-board supply voltage less than 11 volts
* On the E70, there is no REST button (residual heat button). The function of the REST button is integrated into the blower speed button.