Climate Control
Climate Control
Climate control
The following heating and air conditioning systems are described in this functional description:
- Integrated heating/air-conditioning regulation (IHKR)
Single zone internal temperature control with single zone automatic blower control and automatic air distribution control
- Integrated automatic heating / air conditioning system (IHKA)
2.5 zone internal temperature control, with single zone automatic blower control, 2.5 zone automatic air distribution control and sunlight compensation, automatic recirculated air flap control and automatic condensation prevention.
New: The control unit is located on the heating and air-conditioning unit. This separates the heating and air conditioning system control box from the control unit.
The integrated heating and air conditioning system (IHKA) is described in this functional description.
Brief component description
The following components are described:
- Control panel for heating and air conditioning system
- IHKA control unit
- Air conditioning compressor
- Blower motor with blower output stage
- Refrigerant pressure sensor
- Flap motors
- Stratification control wheel
- Temperature sensors
- Automatic air recirculation control sensor
- Rain-light-solar-condensation sensor
- Electric auxiliary heater (diesel fuel only)
Air conditioning control box
New: The heating and air conditioning system control box is no longer an element of the control unit.
The control box is connected to the IHKA control unit through the local interconnect network bus. The control box is supplied by the IHKA control unit using terminal 30F and electronics earth (ground).
The control box connection depends on vehicle equipment levels:
- BMW Business radio:
The heating and air conditioning system control box is directly connected to the IHKA control unit.
- BMW Professional radio and navigation system
The heating and air conditioning system control box is connected to the IHKA control unit through the audio system control box.
Follow diagnosis wiring diagrams.
The control boxes evaluate the operation of the operating elements and transmit the information via the local interconnect network bus to the IHKA control unit.
IHKA control unit
For the first time, the IHKA control unit is connected directly to the heating and air-conditioning unit.
The integrated heating and air conditioning system (IHKA) is operated using the operating elements in the control box. The nominal temperature is set on the control panel separately for the driver's side and front passenger side. The IHKA control unit regulates the climate control to the desired temperature. In doing so, the IHKA control unit picks up the sensor signals and continuously adapts the control variables for delivery temperature and blower output.
The seat heating and heated rear window continue to be operated by buttons in the control panel.
The control unit for the integrated automatic heating / air conditioning system (IHKA control unit) is a bus user on the LIN bus and K-CAN. The front electronic module (FEM) supplies the IHKA control unit using terminal 30F and load earth.
Air conditioning compressor
The air conditioning compressor driven by the engine by means of a belt drive. The air conditioning compressor is switched on and off via a magnetic coupling.
Stepless power control is possible in the air conditioning compressor. Within the A/C compressor, the delivery volume and thus the pressure in the refrigerant circuit is generated by pistons. The piston stroke is controlled by a swash plate.
The electric control valve on the A/C compressor influences the balance of forces on the swash plate and thus the adjustment of the displacement. The front electronic module (FEM) controls the control valve using a switching voltage (pulse-width-modulated). The IHKA control unit prompts the activation. For the purpose of load reduction, only the cooling power that is directly needed is generated.
The magnetic coupling for the air conditioning compressor (diesel engines) is also activated by the front electronic module (FEM).
NOTICE: Air conditioning compressor without magnetic coupling.
Different motorizations have an air conditioning compressor without magnetic coupling.
Blower motor with blower output stage
The blower creates the necessary air mass flow in the heating and air conditioning system. The blower consists of the blower motor, the fan wheel, the blower output stage and the housing.
The integrated heating and air conditioning system control unit (IHKA control unit) specifies the nominal voltage for the blower motor at the blower output stage via the front electronics module (FEM). The nominal voltage is output from the FEM control unit as a signal on the local interconnect network bus. The activation of the blower motor via the blower output stage takes place depending on this control signal.
The blower output stage is diagnosis-capable. The corresponding diagnostic information is transferred to the IHKA control unit via LIN data bus and evaluated there. When there is a threat of overheating for the blower output stage, the output voltage will be reduced, which leads to reduced blower output.
Refrigerant pressure sensor
The refrigerant pressure sensor is electrically connected to the front electronic module (FEM).
The refrigerant pressure sensor for the heating and air conditioning system is fitted in the high pressure line between the capacitor and the evaporator. When cooling, the refrigerant pressure is monitored by the refrigerant pressure sensor and evaluated in the IHKA control unit.
Depending on the sensor signal, the A/C compressor is regulated and/or switched off by the IHKA control unit in the event of excessively high refrigerant pressure. Depending on the refrigerant pressure, a fan setting is determined through the IHKA control unit and transferred to the engine control unit on the bus.
The refrigerant pressure sensor is supplied with 5 V and ground by the front electronic module (FEM).
Flap motors
The flap motors are actuated by the IHKA control unit via the LIN bus and are supplied with power and an earth connection. In the rest state, the control unit switches the supply voltage off.
The flap motors communicate across the LIN bus with the IHKA control unit. The flap motors are switched in series on the LIN bus.
The flap motors in the integrated heating and air conditioning system (IHKA) are all identical. Differences in operation are due only to the respective programmed address. Each flap motor is assigned a certain address. The address determines which function the flap motor assumes in the system network. This address is how the rear compartment flap motor, for example, identifies messages that are addressed to it (e.g. open flap). This address is also how the IHKA control unit, for example, knows which flap motor has issued a fault message.
Prerequisite for successfully addressing the flap motors is correct encoding of the IHKA control unit.
After starting auto-addressing, the last flap motor in the series connection topology is programmed with its address. Then the penultimate flap motor in the topology is programmed with its address and so on until all the addresses have been assigned. Therefore the installation position of the flap motor in the wiring harness decides which address is programmed to the flap motor.
If, for example, the last flap motor in the topology is not connected to the IHKA control unit wiring harness during the auto-addressing process, or there is no connection through the local interconnect network bus: The penultimate flap motor in the topology is wrongly identified as the last flap motor in the topology. As a result this flap motor is assigned the wrong address. The remaining stepper motors also receive the wrong address. The wrong addresses are also assigned if the connectors are mixed up.
If several flap motors are entered in the fault memory with the fault "not responding", then there is probably an open circuit in the connection through the local interconnect network bus. The open circuit (wiring, connector, flap motor) should be looked for in the flap motor that comes first in the topology out of all the flap motors entered.
The following flap motors are installed in the high equipment heating and air conditioning system (IHKA):
- Fresh-air-flap motor
- Front right footwell flap motor
- Defroster flap motor
- Mixing flap motor, right
- Front right stratification-flap motor
- Front left footwell flap motor
- Front left stratification-flap motor
- Mixing flap motor, left
- Rear compartment flap motor
The list order is the same as the activation sequence via the local interconnect network bus. The flap motors are connected to the IHKA control unit by 4-pin plug connections.
The following flap motors are installed for the basic version heating and air conditioning system (IHKR):
- Fresh-air-flap motor
- Mixing flap motor
- Air distribution flap motor
The air distribution flap motor has the task of setting the air distribution over a cam disc. The air distribution flap motor has no way of recognizing the actual position. Despite this, two cams of different widths are provided on the cam disc to allow the cam disc to be unambiguously positioned. A microswitch signals to the control unit that the cams have passed over. This mechanism achieves reliable and rapid positioning of the cam disk.
Stratification control wheel
Two stratification controls are fitted for the IHKA:
- Front centre ventilation grille
- Rear compartment ventilation grille
The selected potentiometer setting is implemented on the flap position of each flap motor.
The signals from the stratification controls are sent to the IHKA control unit along two signal lines. The IHKA control unit evaluates the information and activates the flap motors.
The stratification controls have a liner resistance value determined by the angle of rotation. The limit-position switches are switched on and off mechanically via eccentric washers. Using the limit-position switch, the following ventilation flap positions in the ventilation grille are recorded:
Temperature sensors
Five temperature sensors are installed for the IHKA:
- Ventilation temperature sensor, front left
- Ventilation temperature sensor, front right
- Footwell temperature sensor, left
- Footwell temperature sensor, right
- Evaporator temperature sensor
The temperature sensors measure blow-out temperature directly at the ventilation flaps. The IHKA control unit evaluates the signal from the temperature sensors. The IHKA control unit uses this message to adjust the corresponding flap motors.
The evaporator temperature sensor picks up the outlet temperature of the cooled air at the evaporator to prevent icing of the evaporator.
The temperature sensors are thermistors or NTC resistors ("NTC" stands for "Negative Temperature Coefficient"). NTC resistors can convert the "temperature" value into a resistance� value, which can then be evaluated electronically.
Automatic air recirculation control sensor
The sensor for automatic air recirculation control (AUC sensor) is secured on the microfilter compartment.
The automatic air recirculation control sensor evaluates the concentration of carbon monoxide and nitrogen oxides in the intake fresh air. If the automatic air recirculation control sensor has an emission level that is too high, then the integrated automatic heating / air conditioning system control unit (IHKA control unit) in the air recirculation function is automatically switched to (prerequisite: IHKA in the automatic mode).
Because of the lack of a fresh-air supply, air-recirculation mode is only available for a limited period of time. When the engine is started and the AUC function activated, fresh air is always selected for approx. 40 seconds due to the warming phase of the AUC sensor.
Rain-light-solar-condensation sensor
The rain-light-solar-condensation sensor is in the inside mirror. The sensor is connected to the front electronic module (FEM) through the local interconnect network bus.
The solar sensor and condensation sensor are parts of the rain light solar condensation sensor. The solar sensor enables the integrated automatic heating and air conditioning system (IHKA) to take account of solar irradiation. The solar sensor measures the sunlight on the vehicle. The sunlight on the driver's side and front passenger side are detected separately.
The condensation sensor enables the IHKA to detect window condensation at an early stage, even before the driver can detect it. Counter-measures (program for the prevention of condensation) can be taken in good time without the need for driver intervention.
Electric auxiliary heater
The electric auxiliary heater is a separate component and is installed in the heating and air-conditioning unit. The electric auxiliary heater consists of 4 heat registers. The heat registers are the heat exchange elements of the electric auxiliary heater. Each heat register contains 1 heating element. Air is heated directly by these heating elements and is then fed through the air vents into the passenger compartment. In principle, the electric auxiliary heater works like an electric radiator.
The electric auxiliary heater accelerates the heating of the passenger compartment, especially at low ambient temperatures and during the cold-start phase.
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
System functions
The following system functions are described:
Functional networking
In the following graphic, the functional networking for the integrated automatic heating / air conditioning system is displayed.
Notes for Service department
General notes
Running in the air-conditioning compressor
After replacement of an 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.
This running in can only be carried out with the air conditioning compressor at idle speed. Here, the oil volume filled by the manufacturer mixes evenly with the liquid refrigerant. 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.
Encoding the rain, light and precipitation solar sensor
Encoding of the rain-light-solar-condensation sensor is required after replacement of the windscreen or replacement of a rain-light-solar-condensation sensor.
Also follow diagnosis service functions.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.