The IHKA air-conditioning system is fitted as basis and as high version with different control panels. Information is exchanged between the vehicle components and the IHKA via the K-CAN SYSTEM data bus.
The control panel with control electronics consists of only the most important control elements for the air-conditioning system. It accommodates a temperature sensor with inside sensor fan for recording the interior temperature. The buttons ”HAZARD WARNING LIGHTS” and ”CENTERLOCK” (central locking system) are not evaluated by the IHKA control system.
Precision adjustments of the IHKA functions are carried out at the Control Display (on-board monitor).
The IHKA control unit records the signals of the IHKA components and controls/regulates the heating and air conditioning process. The IHKA control unit causes the heated rear window to be activated and deactivated by the power module. The output stage for the rear roller blind is also incorporated in the IHKA control unit. The data exchange with the DME digital engine electronics for supply/cutoff of the refrigerant compressor is via the K-CAN data bus. The IHKA control unit comes in four versions: Basic and High versions with and without rear window roller blind output stage.
The air conditioner is made up of the following components/functional units:
Blower: The blower is mounted with the blower motor as an assembly. The blower can be detached from the motor. There are versions for left-hand and right-hand drive vehicles.
Regulator: the regulator on the casing of the blower motor is activated by the control electronics in the control panel of the IHKA via the MUX bus and is capable of on-board diagnosis. The diagnosis information is transmitted to the control electronics for evaluation. If on-board diagnosis identifies a fault which would cause components to overheat, the current is reduced or cut off until the fault criterion has been eliminated.
Fresh air flap: The fresh air flap regulates amount of clean air drawn in. The flap is moved by a high-speed drive so that it can be closed in extra-quick time in automatic recirculated air mode (AUC mode). The fresh air flap also serves to compensate ram pressure.
Recirculated air flap: The recirculated air flap is designed as a louvre with three fins. The amount of recirculated air drawn in is regulated with this flap.
Footwell flap: In the Basic version, the footwell flap directs the air flow into the front and rear footwells. In the High version, the front and rear footwells are supplied separately on the left and right.
Rear compartment ventilation flaps: The rear compartment ventilation flaps (separate on left and right) are only fitted in the High version. These flaps serve to adjust the air flow at the rear compartment ventilation outlets and the temperature (rear compartment stratification).
Defrosting flaps: The two linked defrosting flaps serve to regulate the air flow to the windscreen. These flaps are activated jointly in all adjustment and operation functions from the driver's side only.
Hot air/cold air flaps: The hot air/cold air flaps serve to regulate the air flow at the air inlet grilles of the instrument panel and at the B-pillar vents. The temperature is also stratified with these flaps. The combination of the flap pair regulates the air flow and the temperature simultaneously. The functions are separate on the left and right in the High version.
High-speed motors: High-speed motors are only used on the fresh air flaps. The windings of these motors are activated by the control electronics with a stepping frequency of up to 500 Hz.
MUX motors: MUX motors are used on all the other flaps. MUX motors are provided with an integrated circuit for controlling the windings. The integrated circuit is bus- and diagnosis-compatible. All MUX drives are activated by the control electronics via a common motor bus (MUX bus). Faults reported by the integrated circuits are registered in the control electronics and result in the activation being interrupted. The drives are addressed in a manner that cannot be changed and are not interchangeable.
The thermal energy generated by compression of the refrigerant gas in the heat exchanger is dissipated by air cooling to the surroundings at the condenser surface. The refrigerant condenses and turns liquid. In order to prevent corrosion damage, any water present in the refrigerant circuit is bound in the integrated drier. The drier insert can be replaced. It incorporates a filter screen to provided protection against particles.
The compressor compresses the refrigerant gas drawn in by the evaporator and forces it to the condenser. It is always in operation when the vehicle engine is running. Infinitely output regulation is possible on account of its design and activation of a regulating valve with pulse-width-modulated signals by the control electronics. For the purpose of load reduction, only the refrigerating output that is directly needed is generated. Information is exchanged between IHKA and DME via the K-CAN bus.
A microfilter is located in both of the housings for the intake of air. In the Basic version, it is a particle filter while in the High version, it is a combination of particle filter and carbon canister.
The pressure sensor in the pressure line between the condenser and the evaporator supplies the control electronics with signals relating to the system pressure.
The expansion valve is attached to the evaporator. It serves to regulate the amount of liquid refrigerant injected into the evaporator. The liquid refrigerant is metered in such a way that only enough refrigerant as can be fully evaporated is admitted into the evaporator.
The evaporator consists of 27 aluminium plates and has a surface of approx. 5 square metres. Temperature control in the evaporator is performed by the control unit. The evaporator temperature controller operates independently from the other control loops with established controlled variables. The cold air emerging from the evaporator is increased to the desired temperature with the aid of the heat exchanger.
The auxiliary fan is needed to cool the condenser. Its speed is infinitely variable and executed by means of pulse width modulation (PWM). The required fan speed is communicated by the air conditioning via the CAN bus to the DME.
Heat exchanger sensors are installed on the left and right sides in the air flow of the heater for recording the discharge temperature at the heat exchanger. The opening time of the water valves is derived from the values thus determined. The water valves are activated with pulse-width-modulated signals.
The electrically operated auxiliary water pump ensures an adequate water flow at low engine speeds.
An outside air temperature sensor in the area of the bumper measures the outside temperature. The value is used to compensate for the effects of sun radiation on the set temperature in the passenger compartment. The value is transmitted to the IHKA via the K-CAN bus.
In the case of the High version, a solar sensor for measuring external heat sources (e.g. sun rays) is fitted on the dashboard in the grille of the central loudspeaker.