Part I

Integrated Automatic Heating / Air Conditioning System (IHKA)

Integrated automatic heating / air conditioning system (IHKA)
The integrated automatic heating and air conditioning system (IHKA) with left-right separation is a water-regulated heating and air conditioning system.
The following equipment specifications are available:
- Integrated automatic heating and air conditioning system in basis version (IHKA Basis)
The IHKA Basis is an Automatic air conditioning with 2.5 zone control. That means: Left-right separation for driver's and front passenger side and control in the rear (without left right separation)

- Integrated automatic heating and air-conditioning system in High version(IHKA High) with rear automatic rear air-conditioning system (FKA)
The IHKA High with FKA is an automatic air conditioning with 4-zone control. In addition to the left-right separation for the driver and front passenger sides, the FKA also enables a left-right separation in the rear passenger compartment.

- Integrated automatic heating and air-conditioning system in High version (IHKA High) with rear automatic rear air-conditioning system (FKA) and automatic rear air conditioning (HKA)
The IHKA High with FKA and HKA is an automatic air conditioning with 4-zone control. The HKA with left-right separation means that the air supply and air temperature (only cooling possible) in the rear passenger compartment is additionally regulated via the roof air vent.

The major new features of the integrated automatic heating and air conditioning system (IHKA) are:
- Control panel for IHKA is a unit with the control panel for audio
- Fresh air and recirculated air fan of the heating and air conditioning system positioned in the engine compartment
- Ionizer to prevent bacteria growth in the IHKA

Differences between the heating and air conditioning systems (F01, F02):







Brief component description
The following components are described for the heating and air conditioning system:
- IHKA control unit with integrated control panel
- FKA control unit with integrated control panel
- HKA control unit and control panel
- Blower with blower output stage
- Ionizer
- Electric auxiliary heater
- Electric auxiliary heater in the heating and air-conditioning unit (only vehicles with diesel engines)
- Electric auxiliary heater rear left and electric auxiliary heater rear right (only IHKA High with FKA)

- Flap motors
- Stratification control wheel
- Limit-position switch
- Sensors
- Interior temperature sensor (IHKA and FKA)
- Refrigerant pressure sensor
- Evaporator temperature sensor (IHKA and HKA)
- Rain-light-solar-condensation sensor
- Automatic air recirculation control sensor (AUC sensor)
- Heat exchanger sensor
- Ventilation temperature sensor
- Rear-cabin footwell-temperature sensor
- Roof air vent temperature sensor

- Dual water valve
- Refrigerant shutoff valve at front and rear
- Air conditioning compressor
- Condenser with integrated dryer flask
- Expansion valve

IHKA control unit with integrated control panel
The control panel and control unit together form a single component. The control panel of the IHKA forms a unit with the audio control panel.
The IHKA is operated using the operating elements shown in the illustration. The nominal temperature is set on the control panel separately for the driver's and front passenger side. The control unit regulates the climate control to the desired temperature. In doing so, the control unit picks up the sensor signals and continuously adapts the control variables for blow-out temperature and blower output. The seat heating and active seat ventilation (if fitted) are also operated using buttons in the control panel.







FKA control unit with integrated control panel
The control panel and control unit together form a single component. The automatic rear air-conditioning system (FKA) control panel / control unit is fitted in the rear side of the centre console. The FKA is operated using the operating elements shown in the illustration. The nominal temperature is set on the control panel separately for the driver's and rear passenger side. The control unit regulates the climate control to the desired temperature. In doing so, the control unit picks up the sensor signals and continuously adapts the control variables for blow-out temperature and blower output. The rear seat heating and rear active seat ventilation (if fitted) are also operated using buttons in the control panel.







HKA control unit and control panel
The control panel and control unit are installed separately. The control unit of the rear automatic air conditioning (HKA control unit) is installed on the rear air conditioner. The HKA control unit activates the mixing flap drives, the air distribution flap motors, the light-emitting diodes, as well as the blower of the rear air conditioner by means of an output stage.
The left-right separation means that the rear air conditioner has 2 control panels (left-hand control panel on the rear air conditioner and right-hand control panel on the rear air conditioner). A control panel is installed each roof air vent.
The control panels regulate the air supply and air temperature (only cooling possible) in the rear passenger compartment via the two roof air vents.
The left-hand control panel on the rear air conditioner is connected directly via a plug connection to the right-hand control panel on the rear air conditioner. This means that all the settings for the left-hand control panel on the rear air conditioner are picked up and digitized in the electronics of the right-hand control panel on the rear air conditioner. The right-hand control panel on the rear air conditioner sends the signals on the LIN bus to the HKA control unit.







Blower with blower output stage
The blower consists of the blower motor, the fan wheel, the blower output stage and the housing.
Depending on the equipment specification, the following blowers and blower output stages are installed:
- blower with blower output stage(IHKA)
The blower creates the necessary air mass flow in the heating and air conditioning system. At the blower output stage, the control unit of the integrated automatic heating / air-conditioning system (IHKA control unit) specifies the nominal voltage for the blower motor. The nominal voltage is output by the IHKA control unit as a signal on the LIN bus. The activation of the blower motor via the blower output stage takes place depending on this control signal.







- Rear compartment blower with output stage for the rear compartment blower motor (FKA)
The rear compartment blower is installed in the centre console; it generates an additional air mass flow for the rear air conditioning/heating. At the output stage, the control unit of the automatic rear air-conditioning system (FKA control unit) specifies the nominal voltage for the rear compartment blower motor. The nominal voltage from the automatic rear air-conditioning system control unit is to be output to the output stage as a pulse-width modulated signal. The activation of the blower motor via the blower output stage takes place depending on the control signal.







- Blower with blower output stage (rear air conditioner)
The blower creates the necessary air mass flow in the rear air conditioner. At the blower output stage, the control unit of the automatic rear air conditioning (HKA control unit) specifies the nominal voltage for the blower motor. The nominal voltage is output by the rear air conditioner control unit as a signal on the LIN bus. The activation of the blower motor via the blower output stage takes place depending on this control signal.







Ionizer
The ionizer treats the air upstream of the evaporator. The ionizer contains a ceramic plate covered with toughened glass. Electrical conductor paths are attached at the front and at rear side. An AC voltage of approx. 3 kV is applied to the electrode by the control electronics circuit. The application of a device-internal high voltage leads to partial ionization of the air. The reaction generates hydrogen peroxide. The hydrogen peroxide produces a chemical reaction that removes bacteria for the most part from the evaporator and other components of the automatic air conditioning system.
The ionizer is controlled depending on the automatic program as well as the operating condition of the vehicle. The IHKA control unit activates the ionizer by means of a pulse-width modulated signal (PWM signal).







Electric auxiliary heater
The electric auxiliary heater using the PTC principle (resistance with positive temperature coefficient) heats the air flow for controlled-temperature air in the passenger compartment. The electric auxiliary heater accelerates the heating of the passenger compartment, especially at low ambient temperatures and during the cold-start phase. In principle, the electric auxiliary heater works like an electric radiator.
The heating elements in the electric auxiliary heater are PTC resistors. The heating elements are made up of individual ceramic semiconductor resistors. As of a certain temperature, the resistance of the heating element has a positive temperature coefficient. That means: The warmer the heating elements become, the higher their resistance. When the electric auxiliary heater is switched on, a high level of current flows. With increasing heating, this level of current falls. This limits the maximum power consumption. These electrical characteristics of the resistors enable a temperature of approx. 120 °C in the area surrounding the heating elements that presents no problem for the heater/air conditioning system. This "physical" overheat protection is ensured, even in the event of a blower failure.
The following electric auxiliary heaters are installed:
- Electric auxiliary heater in the heating and air-conditioning unit (only vehicles with diesel engines)
The electric auxiliary heater is a separate component and is installed in the heating and air-conditioning unit. The electric auxiliary heater is activated by the control unit of the integrated automatic heating and air-conditioning system (IHKA control unit). Depending on different signals (e.g. temperature signal from the rear footwell temperature sensor, signals from energy management), a percentage power request for the electric auxiliary heater is generated in the IHKA control unit and sent on the LIN bus The maximum electrical power output of the electric auxiliary heater depends on the resources of the vehicle electrical system. As a general principle, only the excess power of the alternator is available to the electric auxiliary heater.







- Electric auxiliary heater in rear left and rear right (only IHKA High with FKA)
The electric auxiliary heaters are part of the rear automatic rear air-conditioning system (FKA) with left - right separation. An electric auxiliary heater is installed In every footwell ventilation duct. Depending on different signals (e.g. temperature signal from the rear-cabin footwell-temperature sensor, signals from energy management), a percentage power request for the electric auxiliary heater is generated in the FKA control unit. The output request in % is transmitted by means of a pulse-width-modulated signal.







Flap motors
The flap motors are activated and supplied with voltage and ground across the LIN bus by the corresponding control unit (IHKA control unit, HKA control unit). In the rest state, the control unit switches the supply voltage off.
The flap motor is fitted with an integrated circuit. This circuit controls the coil of the flap motor. The circuit has bus- and diagnosis capabilities. After activation of the flap motor, the integrated circuit sends position feedback (actual position) to the control unit. The flap motors communicate across the LIN bus with the HKA control unit. The flap motors are switched in series on the LIN bus. Each flap motor is assigned a certain address. The address determines which function the flap motor assumes in the system network. This address tells e.g. the rear right footwell flap motor that messages are being addressed to it (e.g. 'open flap'). This address tells e.g. the IHKA control unit which flap motor has sent it a fault message.