Integrated Heating/Air Conditioning Control (IHKS)
Integrated Heating/Air Conditioning Control (IHKS)
Integrated heating-air conditioner control, IHKS
This functional description covers the integrated heating / air conditioner control. The IHKS can be used to adapt the in-car climate to the individual needs of the passengers. Information is exchanged between the vehicle components involved via the body CAN data bus.
There are no differences for left-hand drive and right-hand drive vehicles. The control unit with operating unit is always fitted in the same position in the vehicle.
The control unit has the following functions (see also individual functional descriptions):
- Temperature control
- Air distribution
- Air flow control
- Recirculated-air mode
- Heated windscreen and rear window
Brief description of components
Control unit with operating unit
The IHKS control unit records the signals of the IHKS components and controls/regulates the heating and air conditioning process. The control unit is at the same time the operating unit of the IHKS.
The IHKS control unit also contains the bank of switches. The bank of switches can be used to operate the seat heating (if installed), the heated windscreen and heated rear window, as well as the electrical power windows. The centerlock button as well as the switches for the fog lamps and rear fog lamp are also built in.
Heater/air conditioner
The IHKS heater / air conditioner is fitted underneath the instrument cluster in the centre, at the front bulkhead.
The heater/air conditioner performs the tasks:
- Generation and regulation of air quantity
- Air distribution, air mixture (stratification) and air dehumidification
- Transfer of refrigerating output generated by the cooling circuit
- Transfer of heat output delivered by the refrigerant circuit
The heater/air conditioner is composed of the following components:
- Evaporator
The evaporator plates are cooled by the coolant evaporating inside. The air-mass flow supplied by the blower is guided over the cool evaporator plates. The air is cooled and dried and guided into the vehicle interior.
- Heat exchanger for heating system
On the IHKS, no heating system heat exchanger sensor is fitted.
- Flaps with drive and mechanical system
The flap motors are connected directly to the IHKS control unit. Three flap motors are fitted in the IHKS. The flaps serve to distribute the air and to mix hot and cold air.
Fresh air recirculated-air flap: the amount of clean air drawn in by the blower is regulated with this flap.
Air distribution flap: The air distribution flap mechanical system mechanically adjusts the air distribution flaps. The air distribution flap mechanical system is driven by the air distribution flap motor. The air distribution flap motor has the task of setting the air distribution by means of a cam disk. The air distribution flap motor has no detection of the actual position. In order to ensure unique positioning of the cam disk nonetheless, there are 2 cams of different widths on the cam disk. The micro-switch signals to the IHKS control unit that the cams have been passed over. This mechanism achieves reliable and rapid positioning of the cam disk.
Temperature mixing flap: The air-mass flow is guided through the evaporator. The air-mass flow is cooled and dried in the evaporator (when the air conditioning system is switched on). Subsequently, the temperature mixing flap guides the air-mass flow (depending on the set desired temperature value in the IHKS controls) fully or partially over the heat exchanger for the heating system and the electrical auxiliary heater (diesel engine).
- Blower with blower ballast resistor
The blower creates the necessary air-mass flow. The blower is fitted after the fresh air recirculated-air flap in the heater/air conditioning system (pressing blower arrangement). The blower ballast resistor enables a manual 4-stage fan setting on the IHKS controls.
- Electrical auxiliary heater
The electrical auxiliary heater based on the PTC principle is fitted in the heater/air conditioner. The electrical auxiliary heater directly heats up the air to adjust the temperature of the vehicle interior. The electrical auxiliary heater is only fitted in diesel engines.
Radiator fan
The radiator fan and the engine cooling are also required for cooling the condenser. The radiator fan is activated by the Digital Engine Electronics.
Signal path:
IHKS control unit -> K-CAN -> Junction box electronics -> PT-CAN -> DME -> Radiator fan
A/C compressor
The air-conditioning compressor compresses the refrigerant taken in by the evaporator. The refrigerant is pressed towards the condenser. The air-conditioning compressor is switched by the compressor coupling. Activation is initiated by the IHKS control unit.
Condenser with integrated drier flask
In the condenser, gaseous refrigerant is converted into liquid refrigerant. In the integrated downstream drier flask, any water present in the refrigerant circuit is bound. The drier insert can be replaced.
Sensors
- Evaporator temperature sensor
The evaporator temperature sensor measures the outlet temperature of the air at the evaporator to prevent freezing over. The evaporator temperature sensor is directly connected to the IHKS control unit.
- Coolant pressure sensor
The coolant pressure sensor is fitted in the pressure line between the condenser and the evaporator. Depending on the sensor signal, the air-conditioning compressor is regulated by the IHKS control unit in the event of excessive refrigerant pressure. The junction box supplies the coolant pressure sensor with voltage. The data is evaluated in the junction box electronics. The prepared data is sent across the body CAN (K-CAN) to the IHKS control unit.
Microfilter
A microfilter with activated carbon is built into the IHKS. The activated carbon filter makes an additional contribution to cleaning the fresh air that enters of gaseous pollutant emissions. The state of the microfilter is not picked up.
Notes for Service department
Observe the following information for service:
General information
The following general data is provided for servicing the IHKS:
Running in the air-conditioning compressor
IMPORTANT: After replacement, allow the air-conditioning compressor to run in.
After replacement of the air-conditioning compressor or refilling the refrigerant circuit, the air-conditioning compressor must be run in. Running in is required to ensure lubrication (oil distribution). Running in can only be carried out using the BMW diagnosis system.
For this running in, the air-conditioning compressor must be operated within the specified engine speed range. Here, the oil volume filled by the manufacturer mixes evenly with the liquid refrigerant.
IMPORTANT: Do not exceed the specified engine speed.
If the engine speed exceeds the specified engine speed range, running in is aborted automatically. The running-in procedure must then be repeated in its entirety.
Replacement of the electrical auxiliary heater
The electrical auxiliary heater can be replaced in service (the heater/air conditioner must be completely removed).
Coding and programming
Coding
When coding the vehicle-specific data, the following details (among others) are taken into account:
- Engine variant (diesel engine or petrol engine)
- Version of the control unit (IHKS)
Programming
Flash programming of IHKS control unit via the K-CAN is possible.
No liability can be accepted for printing or other errors. Subject to changes of a technical nature