System Overview
System Overview
The heating and air conditioning system spans the entire vehicle. The major component locations including the optional rear air conditioner (E66) with cooler box is shown below.
Overview of System Components
Refrigerant System: The refrigerant system components include the following.
The layout includes two shutoff valves (one at the front for IHKA and one at the rear for E66 IHKA) and an additional evaporator with expansion valve. R134a refrigerant is used in the E65/E66. The system capacity is 1.78 ± .02 lbs (810 ± 10 grams).
Heating System: Components of the heating circuit (coolant) with the N62 engine include:
Air Ducts: Air ducts refers to all components that distribute the air supplied by the fan to the outlets. The ends of the air ducts are fitted with directional grilles.
Heater and Air Conditioner Housing: The IHKA housing is secured to the middle of the engine compartment bulkhead, underneath the instrument panel. The blower is mounted inside the passenger compartment offset to the passenger's side (in front of the glovebox).
The IHKA housing is the central unit in the heating and air conditioning system, it performs the following functions:
- Create and control air flow
- Distribute the air
- Mix the air (air stratification)
- Dehumidify the air
- Convert the energy supplied by the cooling system
- Transfer the refrigeration power of the refrigerant system
Control Panel/Control Module: The control panel is a dashboard insert with integrated electronic controls. The electronic circuits monitor and control the entire IHKA system. The control panel provides the essential basic controls. Precision adjustments are made using the Controller and the Control Display menu settings.
There are also controls for the hazard warning lights and central locking (Centerlock) functions (not part Of IHKA system, only for location convenience).
Functional Overview:
Additional Sensors and Actuating Components: The system includes other components in addition to those previously listed.
- AUC-2 sensor for automatic recirculated air control
- One solar sensor for each side
- One temperature sensor on each side in the center vent outlets
- One potentiometer on each side in the rear center outlets (for adjusting air stratification)
- One limit position switch on each side in the rear compartment center outlets
AUC-2 Sensor: The AUC-2 sensor provides an input to the IHKA module that will automatically activate recirculation mode when excessive ambient pollution is detected. This sensor detects pollutant gases emitted by gasoline and diesel engines that include the following:
- Hydrocarbons
- Carbon monoxide
- Nitrogen oxides
The heating and electronic analyzer (and software) are integrated into the sensor (located on the fan shroud). The sensor signal is pulse width modulated (PWM) to the IHKA control module.
The sensor is self diagnosable. Within the first minute of operation it determines if there is a fault in the sensor electronics. A fault will be set in the IHKA control module when a fault is detected.
Solar Sensor: The solar sensor is mounted on the dashboard top center grille. The black cap is visible which masks the diffuser and two (left and right) photo resistors. The cap only allows infrared light to pass through.
The solar sensor supplies the control module with a separate signal for left and right. These signal levels depend on the intensity of the sunlight striking the sensor. The solar sensor influences:
- Blower output
- Opening angle of the ventilation flaps
- Air stratification temperature
Temperature Sensors: The various temperature readings used by the IHKA control module are supplied from the following sensors:
In the Heater and Air Conditioner Housing
- Evaporator temperature sensor
- Two heat exchanger temperature sensors
In the Control Panel
- Interior temperature sensor with blower
On the Vehicle
- Exterior temperature sensor (signal provided over the K-CAN bus)
- Center air outlet grill of the dashboard (one temperature sensor for each side, 1 right)
Each temperature sensor consists of a Negative Temperature Coefficient (NTC) unit in a plastic housing with injection molded connectors. The IHKA control module interprets the varying analog voltage signals as changing temperature. The NTC units used for evaporator and heat exchanger have different resistances, so the holders are mechanically coded to ensure that the sensors cannot be installed in the wrong location.
Microfilter System (Air Intake): There is a microfilter in each of the two air intake filter housings. The microfilters are a combination of particle filter and activated charcoal filter. The activated charcoal filters out unhealthy and noxious gases from the intake air before it enters the heater and air conditioner housing.
The service life of the filter depends on the degree of air pollution in the operating environment. The automatic recirculated air control function (AUC) with the filtration system provides optimum protection for the occupants of the car. The AUC function also prolongs the service life of the filter.