IHKA Climate Control
IHKA Climate Control
The IHKA heater/air conditioner in the E46 is similar to the system currently installed in the E36. Design and component changes were made to improve the overall performance and operation of the system. This section will deal with the changes and highlights of the E46 IHKA system. New features of the IHKA system include:
- New Control Panel/Module
- Single heater core for temperature regulation
- M-Bus Control of all stepper motors
- New fresh air micro filter
- Regulated A/C compressor
- Regulated [1][2]auxiliary fan operation
- Heater Control Personalization
Control Panel
All heating and air conditioning functions are carried out at the control panel. The panel has changed as follows:
- The three manual air distribution buttons are located on the left side of the panel for upface vent and footwell distribution.
- The automatic air distribution button is located on the bottom of the panel along with the temperature control - blower speed control and recirculation control buttons.
- The defrost, air conditions request and rear window defogger buttons are located on the right side of the panel.
- The LCD matrix displays the requested temperature setting and blower speeds as on the previous system. There is now only one setting for temperature control.
- The interior temperature sensor and blower fan are located on the left side of the LCD matrix.
Fresh Air Micro Filter
The fresh air micro filter is installed in the fresh air inlet of the engine compartment. The filter can be serviced quickly by removing the plastic cover and removing the filter.
Temperature Regulation - Heating
The E46 uses one water valve/heater core as part of interior temperature regulation. The water valve is pulsed to control the flow of coolant through the heater core as on other systems.
Temperature regulation is based on the inputs from:
- Temperature control switch
- Interior temperature sensor
- Ambient temperature signal
- Heater core sensor
- Evaporator temperature signal
- "Y" factor
The rocker switch is used to select the desired cabin temperature which is displayed in the matrix of the control panel. The range for temperature display is from 60 to 90 °F.
SERVICE STATION FEATURE - The "Service Station" feature introduced with the E38 IHKA is now integrated into the E46 IHKA. This prevents the heater core from being flooded with hot coolant when refueling the vehicle.
Temperature Regulation cooling
Air conditioning control on the E46 is similar to the E39 IHKA system. The system uses the variable displacement compressor introduced on the E39. The swash plate of the compressor is hinged so that is can vary the piston travel based on the output requirements of the system.
Compressor Control
Control of the A/C compressor is a function of the MS42.0 engine control module as in the past. However, the control has changed to include the regulated [1][2]auxiliary fan operation.
Pressing the snowflake button is a request for A/C activation. As long as the evaporator temperature is Above 36 °F, the IHKA will signal the MS42.0 control module to activate the compressor.
The IHKA control module sends the following signals to the MS42.0 over the K-Bus and CAN Bus via the instrument cluster:
- Request for A/C activation (signal KO)
- Load torque for switching the compressor on
- Requested [1][2]auxiliary fan speed
The IHKA determines the load torque for compressor activation and required [1][2]auxiliary fan speed from the pressure sensor mounted on the receiver/dryer.
The pressure sensor provides a linear voltage input signal (0 - 5 volts) to the IHKA control module. The IHKA processes this signal and determines the load torque of the system (0 to 30 Nm with a variable displacement compressor). The higher the pressure in the system, the higher the voltage input signal to the IHKA.
The output signal to the MS42.0 will enable the engine control module to modify the idle speed, timing and fuel injection amount based on the load that will be imposed when the compressor is activated.
The [1][2]auxiliary fan is now a variable speed fan (15 stages) based on the system load. The MS 42 will activate the fan through a pulse modulated final stage control.
Stepper Motor M-Bus Control
The E46 continues to use the M-Bus for stepper motor control. All five stepper motors of the IHKA are now bus controlled including:
- Two fresh air/recirc-air flap motors
- Face vent flap motor
- Footwell flap motor
- Defrost flap motor
Due to the requirement for a fast acting motor for the fresh/recirc flaps, two different stepper motors (slow/fast) are used in the system.
IHKA Personalization
The newly introduced features of Car/Key Memory allow various functions/features of the IHKA control to be tailored to the individual owner's/driver's wishes.
Car/Key Memory is covered in the ZKE V section.
The functions of the IHKA that can be programmed to the owner's/driver's wishes include:
- Automatic activation of recirc when the vehicle is started
- Adjustment (raising/lowering) of the blower speed
- Automatic opening of the ventilation flaps with warm coolant
- Automatic closing of the footwell flap with A/C activation
- Automatic closing of the defroster flaps with A/C activation
- Correction of the set temperature (raise/lower)
- Automatic activation of the compressor control when the ignition is switched on
- Auto program for the blower control when the ignition is switched on
These features are programmed using the coding/programming function of the DIS/MoDiC.
System Operation
The balance of the E46 IHKA system's features and operation carry over from the E36 including:
- Maximum defrost operation
- Rear window defogger operation
- Final stage blower control
- Road speed dependent fresh air flap operation
- Air distribution control
- Stepper motor calibration run
- Cold start interlock
Diagnosis Troubleshooting
The "self diagnostics" of the IHKA control module monitors the status of inputs and outputs of the system. If a fault is detected, it is initially entered in RAM and than in the EEPROM when the ignition is switched off. If available, a replacement value will be activated when various sensor faults are detected as with previous systems. A maximum of six faults can be stored in the EEPROM when the ignition is switched off.
The E46 IHKA is connected to the diagnostic link via the K -Bus/instrument cluster. The system uses the E46 "Fault Symptom Troubleshooting " procedures for troubleshooting problems and faults with the system.
When troubleshooting problems with the E46 IHKA, it is important to note that because the Car/Key Memory feature can change the functionality of the system, a review of the setting should be performed prior to condemning a component as faulty.