Temperature control IHKA

Temperature control IHKA

This functional description covers the temperature control of the integrated automatic heating / climate control, IHKA. The IHKA is a heating and air conditioning system regulated on the on air side. The interior temperature is picked up by two independent temperature sensors. The sunlight level is picked up by the solar sensor.

Brief description of components

Temperature control buttons

The following buttons are on the operating unit:

• Temperature dial
  The temperature dial is used to set the desired nominal temperature. The selected nominal temperature is displayed in the IHKA display. The minimum temperature adjustment is shown in the display with ”LO”; the maximum temperature adjustment with ”HI”.
  
• A/C button
  Pressing the A/C button sends the request to switch on the air-conditioning compressor to the junction box electronics. Depending on the vehicle status, the air-conditioning compressor is activated and the function LED in the A/C button lights up.
  
• MAX button
  Pressing the MAX button sets the maximum cooling output. The air-conditioning function is switched on (if not yet active). The blower output is maximised. In the display, the temperature display is switched to ”LO”. ”MAX *” is displayed. After deactivating of the MAX function, a calibration to the normal operating mode is carried out.
  
• AUTO button
  Pressing the AUTO button switches the IHKA into automatic mode. The air distribution, blower control as well as temperature control are handled automatically by the IHKA control unit.
  

Sensors

• Internal temperature sensor
  The internal temperature sensor is built into the IHKA control unit. The internal temperature sensor measures the temperature in the control unit. This measured temperature is used by an integrated mathematical model to calculate the value for the interior temperature.
  The internal temperature sensor is not force-ventilated. This means that no internal temperature sensor fan is fitted in the IHKA control unit.
  
  Note: The value displayed in the BMW diagnosis system for the inside temperature deviates very strongly from the perceived temperature value and the set desired temperature value. This measured value is processed internally in the IHKA control unit and adapted for the control operation.
  
• Ventilation temperature sensor
  The ventilation temperature sensor is integrated in the solar sensor. The ventilation temperature sensor measures the delivery temperature directly at the upper ventilation air vents.
  
• Solar sensor
  The solar sensor consists of a photo diode. The solar sensor picks up external light or heat sources (e.g. sunlight). The solar sensor provides the IHKA control unit with an analog signal depending the intensity of the sunlight in each case.
  Adaptation to the sunlight is only active in the automatic program. The solar sensor is fitted in the centre of the instrument panel.
  
• 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 IHKA 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 IHKA 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 IHKA control unit.
  

System functions

Temperature control

A master controller handles the temperature control in the vehicle interior. The control operation is based on the set nominal value and the calculated actual temperature value. The nominal value is set at the IHKA controls via the temperature dial. The actual value is calculated from the measured temperature of the internal temperature sensor and of the ventilation temperature sensor, as well as the measured value of the solar sensor. The lead parameter results from the comparison of the actual value of the inside temperature with the corrected nominal value.

Compared to the set nominal value, when it is cold the inside temperature is raised so that even at subzero temperatures the climate remains pleasant even with an unchanged temperature setting. The outside temperature is transferred across the body CAN to the IHKA control unit.

The ventilation temperature is regulated by the mixing flap in the heater/air conditioner. The air-mass flow is guided through the evaporator. The air-mass flow is cooled and dried (when the air conditioning system is switched on). Subsequently, the mixing flap guides the air-mass flow (depending on the set desired temperature value in the IHKA controls) fully or partially over the heat exchanger for the heating system and the electrical auxiliary heater. Subsequently, the air flows mix once again. The air-mass flow is then guided via the ventilation flaps into the vehicle interior.

The evaporator temperature is regulated with the help of the evaporator temperature sensor and the expansion valve. The evaporator temperature is adjusted to the specified nominal value of 2 °C. Lower temperature are not possible due to the danger of freezing over. The evaporator control is independent of the temperature control in the vehicle interior.

Interior control

The temperature dial is used to set the nominal temperature. Turning upwards increases the nominal temperature; turning downwards lowers it. The useful temperature range is from 16 °C to 32 °C.

With a target value position of 32 °C [90 °F], the function MAX HEATING is activated. In the display, "HI" is displayed instead of the temperature value. The blower output is maximised. Interior control is thereby cancelled. The heat-exchanger temperature is regulated to the maximum temperature.

With a target value position of 16 °C [60 °F], the function MAX COOLING is activated. In the display, "LO" is displayed instead of the temperature value. The blower output is maximised. Interior control is thereby cancelled. The heat-exchanger temperature is reduced to the minimum temperature.

Notes for Service department

Observe the following information for service:

General information

The following general data is provided for servicing the IHKA:

Replacement of the electrical auxiliary heater

The electrical auxiliary heater can be replaced in service (the heater/air conditioner must be completely removed).

Diagnosis instructions

The following diagnosis instructions are provided for servicing the IHKA:

Internal temperature sensor

The value displayed in the BMW diagnosis system for the inside temperature deviates very strongly from the perceived temperature value and the set desired temperature value. This measured value is processed internally in the IHKA control unit and adapted for the control operation.

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 (IHKA)
    
• Programming
  Flash programming of the IHKA control unit via the K-CAN is possible.
  

Car and Key Memory

Almost all functions of the Car and Key Memory are set in the vehicle itself (see Owner's Handbook at ”Personal Profile”: personal settings for a maximum of 3 remote controls via the display in the instrument cluster or the Central Information Display).

Country-specific versions

The temperature display can be switched to °C or °F using the on-board computer function.

No liability can be accepted for printing or other errors. Subject to changes of a technical nature