Table of Contents

Table of Contents
Table of Contents
IHKA Automatic Heating and Air Conditioning System
Objectives of the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Purpose of the System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Air Conditioning System
System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Workshop Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Heating System
System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
IHKA Heater and Air Conditioner Housing
System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Control Panel/Control Module
Detailed Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Temperature and Air Flow Control
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Air Distribution
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Stationary Functions
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Non-Air Conditioning Functions
Rear Roller Blind Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48
Key Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Vehicle Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Workshop Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Review Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
IHKA Automatic Heating and Air Conditioning System
Model: E65 - 745i / E66 - 745Li
Production Date: 11/2001 - E65, 01/2002 - E66
Objectives of The Module
After Completing this module, you will be able to:
• List the gasses detected by the AUC-2 sensor.
• Explain how the refrigerant compressor output is varied.
• List the refrigerant compressor “Run In” procedure.
• Locate the blower motor and blower control module.
• Describe the control panel functions.
• Explain the “Y” factor.
• Explain how the temperature is increased during air conditioning operation.
• List the functions that apply to heater operation when the coolant is cold.
• Demonstrate Manual Air Distribution individual adjustments.
IHKA Automatic Heating and Air Conditioning System
Purpose of The System
The E65 IHKA automatic heating and air conditioning system is designed with technological improvements and new or modified functions. The design objectives for the E65 IHKA
system meets the requirements of customers worldwide for heating and cooling capability.
The control display provides indication and operation.
Important primary functions are
controlled by basic knobs and
pushbuttons on the control panel
which includes:
Temperature control
Blower speed
Recirculating air
Maximum Air Conditioning
Rear window defogger
Automatic functions
1. IHKA Control Panel/Module
4. Face Vent Outlets
3. Upper Air Flow Outlets (defrost)
5. Front Footwell Outlets
Customer Benefits:
Straightforward understandable operation.
Individual adjustment is possible using the virtual controls in the control display.
Individual settings are stored in memory.
The rear seating area has air inlet grilles in the center console and in the B pillars.
The design allows direct and indirect air flow to all occupants.
Individually adjustable temperature stratification (warm/cold).
Consideration for warm and cold air distribution (head, chest and leg regions).
The system prevents drafts.
Primary function controls are grouped in a single unit that is readily visible and accessible to the driver and front seat passenger.
• The temperable ventilation (air stratification) is controlled by adjusting elements in the air
inlet grilles and the control display.
IHKA automatic heating and air conditioning system features:
Activated charcoal inlet air micro-filter
Recirculation air filter
Residual heat
Independent ventilation
AUC-2 sensor (gas sensor for automatic recirculation air control)
2 separate drives for outside air/recirculated air
Air outlets in the B-pillars for rear passengers
Solar sensor
Vehicle and Key Memory for blower and temperature
Dual temperature control (left/right)
Automatic air distribution
Air flow control
Ventilation temperature stratification using the Controller in the Control Display menu
Rear seat ventilation temperature control by the knurled knobs
E65 innovations:
Refrigerant Circuit
• Clutch-less refrigerant compressor is regulated externally by a pulse width modulation
(PWM signal).
• Dryer integrated into condenser.
Heater Circuit
• Auxiliary water pump is separate from dual water valve and installed in a remote position
(easier to fill and bleed).
• Heater supply is from upper radiator hose for better accessibility and pressure limitation.
IHKA Air Conditioner
Layout with offset positioned blower unit.
Modified functionality of the flap system for air flow control and stratification.
Blower with single fan impeller.
Blower control module (clock regulator with K-Bus and diagnosis capabilities).
Flap drives (stepper motors) with blockage recognition.
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.
1. Heater and Air Conditioner housing assembly
2. Rear air conditioner with cooler box (E66 only)
3. Condenser
(Not shown: refrigerant compressor and auxiliary fan)
Overview of System Components
Refrigerant System: The refrigerant system components include the following:
1. Auxiliary fan with shroud
2. Condenser (2a) with integrated dryer (2b)
3. Refrigerant compressor
4. Pressure sensor (in the line)
5. Fill adapter pipe
6. Interface connection at bulkhead
7. Evaporator (inside the housing)
8. Shutoff valve (rear AC - E66)
9. Expansion valve
10. Pressure and suction lines for IHKA
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. The system capacity is 1.78 +/- .02 lbs (810 +/- 10 grams).
Heating System: Components of the heating circuit (coolant) with the N62 engine include:
1. Return hose
2. Heat exchanger
3. Supply hose
4. Supply hose
5. Dual water valves
6. Electric auxiliary water pump
7. Supply hose
8. Hot coolant supply hose
9. Radiator
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.
1. Air intake/filter housing
2. Defroster ducts
3. Ventilation ducts
4. B-pillar ventilation
5. Front footwell ducts
6. Outlet ducts in the instrument panel
7. Ventilation for rear seating area
8. Heating ducts for rear seating area
9. Side window air ducts
10. Heater/Air Conditioner housing
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
Layout of the IHKA major components (as viewed from the back)
1. Defroster duct
11. Blower motor
2. Drive, warm air left
12. Blower control module
3. Ventilation, left
13. Evaporator
4. Heating exchanger
14. Condensation drain
5. Drive, defroster
15. Drive, footwell
6. Drive, cold air right
16. Drive, rear compartment ventilation
7. Drive, warm air right
17. Rear seat area duct, left, ventilation
8. Drive, recirculated air
18. Footwell/rear seat area outlet, left
9. Drive, fresh air
19. Footwell outlet, front left
10. Recirculated air flap
20. Drive, cold air left
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.
IHKA control panel front view
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:
DME (ECM) - Digital motor electronics
PT-CAN - Bus cable
K-CAN - Bus cable
ZGM - Central gateway module
MMI - control display
TM - Door module
SH ZH - auxiliary heating
IHKA - E66 rear air conditioner
PM - power module
CAS - car access system
ECU - IHKA control module
LSZ - light switch center
M PWR - stepper motors
HR - rear window roller blind
I/Os - inputs/outputs
S-Sen - solar sensor
AUCI/II-Sen - AUC I and AUC II sensors
B-Sen - fogging sensors (future)
S1 - limit position switch
Poti - adjusting potentiometer
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
• 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.
1. Inducted particles and gases
2. Particle filter (prefilter)
3. Micro-fiber matting
4. Carrier material
5. Activated charcoal filter
6. Covering layers, activated charcoal
Air Conditioning System
System Components
Refrigerant Compressor (KMV): The refrigerant compressor compresses the refrigerant
gas inducted from the evaporator and forces it to the condenser. The compressor does not
have a clutch and it always operates when the engine is running. The compressor output
is variable and is controlled internally by signals from the IHKA control module.
Delivery rate and pressure is produced by
seven pistons. The piston stroke is influenced
by a swash plate.
1. Solenoid valve
2. Hollow piston (Teflon coated)
3. Swash plate (MoS2 coated)
4. Belt pulley
5. Rubber elements
Clutchless Drive Advantages:
Application and Function:
• Compact
• Saves Weight
• No electric power consumption
• Vibration damping function
• Torque transmission
• Protective function in the event of a
The illustration (right) shows the design of the
refrigerant compressor drive with rubber elements.
1. Splines in the drive hub
2. Drive hub contour
3. Splined shaft
4. Rubber elements
5. Belt pulley
The rubber elements mesh with drive hub contour and will deform to give way (slip) if the
compressor seizes.
The position of the swash plate is varied by the internal pressure which is controlled by the
electric control valve integrated into the compressor. The control valve influences the force
at the swash plate by changing the crankcase chamber pressure (PC). When de-energized
(control valve open), the swash plate is almost vertical and not deflected. The compressor
output is approximately 0 - 2% which is required to maintain internal lubrication.
The IHKA control module sends a pulse width modulated signal (12V, 0.85A at 400 Hz) to
close the control valve. This causes the pressure in the crankcase chamber to diminish. The
swash plate is deflected (angled) and the compressor output increases (variable between
2 - 100%).
1. Orifice between crank case chamber
pressure Pc and intake pressure Ps
5. Coil
6. Valve tappet
2. Crankcase chamber pressure Pc
7. High pressure Pd
3. Gas flow
8. Bellows with spring 1
4. Spring 2
9. Intake pressure Ps
Condenser with Dryer: Compressing the refrigerant gas in the compressor causes the
temperature to rise. This heat energy is dissipated to the environment by air cooling the surface of the condenser. which causes the refrigerant to condenses and become liquid.
Any moisture that might be present in the system is trapped in the integral dryer to avoid corrosion damage in the refrigerant system.
The dryer insert (1) is replaceable. The granulated desiccant can absorb up to a maximum of 8
grams of water.
It is important to keep the refrigerant system
sealed for as long as possible when performing
Auxiliary Fan (ZL): The auxiliary fan (approx. 420 mm diameter) has 5 asymmetrically rearward curved blades. The motor is the brushless type with electronic commutation (no
brushes to wear). The fan speed is variable from 30 to 100%. The required fan speed is
requested by the IHKA to the ECM over the CAN bus.
The ECM sends a PWM control signal to the fan motor final stage (integrated into the fan
housing). At lower speeds and standstill (engine idling) cooling is assisted and maintained
by the auxiliary fan.
The auxiliary fan is deactivated at vehicle speeds > 80 km/h (fan stage 0 is output). At higher vehicle speeds, ram air is sufficient to cool the condenser. The auxiliary fan is activated
when the vehicle speed drops below 70 km/h. The operating stage depends on the refrigerant pressure. There are 15 possible speeds depending on refrigerant system pressures.
Pressure Sensor: The pressure sensor is in
the pressure line between condenser and the
The sensor sends the IHKA control module an
analog signal between 0.4V and 4.6V as a representation of system pressure.
The 5V supply is provided by the IHKA control
module and the sensor current consumption is
< 20 mA.
Expansion Valve: The block type expansion valve in the E65 functions the same as models currently in use. The expansion valve is mounted directly on the evaporator in the air
conditioner housing (accessable from the driver’s side) and controls the inlet rate of liquefied refrigerant into the evaporator.
This ensures that the evaporator receives only as
much liquefied refrigerant as it can evaporate
(supply side = liquid/blue, outlet side = gas/red).
1. From evaporator
2. To evaporator
3. From condenser
4. To refrigerant compressor
Evaporator: The evaporator is an aluminum
plate type surface that consists of 27 plates
with a total surface area of approximately 5
square meters. To avoid corrosion, the evaporator has a very thin coating to speed condensation drain off.
Cooling the air causes some of the contained
moisture (humidity) to condense, so the evaporator control is set not to drop below approximately 2 ºC in order to prevent ice from forming.
The temperature is monitored by the evaporator
temperature sensor.
Principle of Operation
Evaporator Temperature Control and Refrigerant Circuit Monitoring
The evaporator temperature control keeps the evaporator temperature at a constant 2 ºC
and operates independently of the other control circuits. The variable output to the refrigerant compressor is derived from or limited by the following criteria:
Difference between requested setting and actual value of the evaporator temperature
Compressor speed
Coolant temperature
Compressor load torque
Torque limitation
Refrigerant pressure limitation
Kick down (vehicle acceleration)
Battery voltage
Requested Setting and Actual Evaporator Temperature Difference
The cold air exiting from the evaporator is reheated to the desired temperature by the heat
exchanger. To control ventilation, the measured evaporator temperature is used as an influencing variable to compute the angle of the cold air flap.
Refrigerant Compressor
The compressor is activated on demand when all switch on criteria is met. It is an internally regulated and externally controlled compressor. The control valve is the manipulated by
a variable PWM (400 Hz) signal to ensure that only the refrigeration required at a given time
is generated by the compressor. This reduces the load when full cooling power is not needed.
Compressor Speed
K-CAN messages provide the IHKA with engine speed information (from the ECM) which
represents compressor speed.
Compressor Load Torque
The variable load torque is derived from the evaporator temperatures (requested setting
and actual) by the IHKA to generate the PWM signal for the solenoid valve to deflect the
swash plate. The physical compressor load torque requirement is calculated by the IHKA
control module and sent to the ECM over the K-CAN Bus.
Torque Limitation
The IHKA receives a K-CAN message from the ECM containing a maximum specified
torque. Under full throttle/kick down and at high coolant temperatures, the ECM uses this
signal to restrict the maximum possible compressor load torque.
Refrigerant Pressure Limitation
The refrigerant pressure is monitored through the pressure sensor to avoid excessive system high side pressures. The IHKA limits refrigerating power linearly from 100% to 0%
(shutdown) between 22 to 28 bar of pressure.
The compressor is deactivated when the pressure is < 1.8 bar. The compressor is reactivated when the pressure is > 2 bar, provided that all the other switch on criteria is met.
Compressor - Running In
When the compressor is operated for the first time it must be run in to ensure proper lubrication (oil distribution). During the Running In procedure the compressor must be operated at speeds between 300 to 1200 rpm.
If the speed drops below 300 rpm or rises above 1200 rpm during the Running In phase,
it is interrupted and automatically resumed after a delay of 5 seconds (refer to Service
Communication between IHKA and the ECM
The IHKA notifies the ECM of the request for compressor activation in a K-CAN message
(Control A/C ready).
In anticipation of the compressor load and based on the outside temperature, this is
accomplished by increasing engine idle speed from 550 to 750 rpm.
There are three different switching criteria:
0 = No air conditioning required, system ON
1 = Air conditioning required, system ON without speed increase
2 = Air conditioning required, system ON with speed increase
The ECM provides the IHKA with a torque of 30 Nm, provided that deactivation criteria
does not apply (high coolant temperature, kick-down, etc.). The IHKA will activate the
refrigerant compressor in the permitted torque range and reports the actual torque applied
back to the ECM.
Limitation of Compressor activation by the ECM
The ECM sends a K-CAN message notifying the IHKA of the maximum available torque. If
this maximum available torque is less than the current compressor load torque, the valve
signal is reduced until the load of the compressor drops to or below this value. If this can
not be accomplished by the minimum valve signal, the compressor is shut down.
Workshop Hints
Initial Operation after Replacing the Refrigerant Compressor
When the compressor is operated for the first time (after replacement) it must be run in to
ensure proper lubrication (oil distribution)!
1. Set all air vents in the instrument panel to "OPEN".
2. Start the engine and wait until it stabilizes at a constant idle speed.
3. Set the speed blower to at least 75% of the maximum output.
4. Switch on the A/C system and allow it to operate for at least 2 minutes at idle speed
(risk of damage at higher speed).
Note: The engine speed must not exceed 1200 rpm. If it does, the procedure will automatically abort and must be repeated.
Consult the Repair Information (in TIS) for the correct compressor oil filling procedure and
the Running In phase that allows thorough and uniform mixing with the refrigerant.
Heating System
System Components
Auxiliary Water Pump (ZWP): The ZWP is a rotary pump with an electronically commuted direct current motor. The pump housing is sealed from the motor. Drive from the motor
is transmitted to the impeller through the sealing partition.
The ZWP is protected against blockage and reverse polarity.
In the event of a thermal overload, power is reduced down to
intermittent operation.
The ZWP enhances hot water flow (1 - outlet, 2 - inlet) and
ensures the minimum flow rate, particularly when the engine
is idling or off (residual heat function).
Dual Water Valve (WV): The dual water valve operates electromagnetically to meter the
volume of coolant flow to the left and right heat exchangers.
This function is performed by an open/close ratio that the
IHKA control module varies according to the demand. The
valves are sprung open when de-energized.
1. Left heat exchanger circuit
2. Hot coolant inlet
3. Right heat exchanger circuit
Heat Exchanger (WT): The aluminum heat exchanger is the flat tube type consisting of
two halves (left and right) with one inlet for each and a common outlet. It transfers the thermal energy supplied by the flow of heated coolant to the air flowing through.
Under ideal conditions as much as 10 kW of heating power
can be produced.
There are two heat-exchanger temperature sensors located in
the air stream (left/right) that measure the exiting air temperature.
IHKA Heater and Air Conditioner Housing
System Components
The Heater and Air Conditioner Housing consists of the following components/functional
• Evaporator/evaporator sensor
• Heat exchanger/sensor
• Blower
• Blower speed control module
• Flaps/flap actuating mechanism
• Flap drives/stepper motors
Flap Drives:
1. Warm air left
2. Defrost
3. Fresh air
4. Recirculated air
5. Warm air right
6. Cold air right
7. Footwell right
8. Rear seating area right
9. Rear seating area left
10. Footwell left
11. Cold air left
Blower: The blower assembly is a radial flow
blower with a fan impeller on one side. It is
mounted with the blower motor in a sound
proofed housing (1), offset to the passenger’s
side. The blower control module can be separated from the motor.
The blower produces the required air mass
flow and under ideal conditions can achieve a
maximum flow rate of approximately 9 kg/min.
Depending on the positions of the air flow control flaps, the required quantity of air is inducted either through the fresh air filters or through the recirculated air flap depending on the
operating status.
Technical data of the blower motor:
Permanent Direct current motor
12 V
Rated speed
3350 rpm
Rated current consumption
27 A
Blower Control Module: The blower control module is
mounted directly on the blower motor housing. It has self
diagnosis capabilities and is addressed by the IHKA control
module over the K-bus (view from below inside open IHKA
1. Blower control module
2. Blower
The blower control module uses a “clocked” regulator which
reduces control power losses. This significantly saves energy
and requires a smaller heat sink.
The diagnostic information is transmitted to the IHKA control
module for processing. If a fault is detected in the regulator or
blower that would cause an overload (overheat), current is
reduced or the blower is temporarily shut down.
Flaps/Flap Actuating Mechanism: The flaps distribute the air and mix cold air with warm
air. The flap actuating mechanism includes the flaps, corresponding shafts with lever
assemblies and the drive motors.
The flaps in the IHKA are as follows:
Fresh Air Flap: This flap regulates the quantity of fresh air inducted by the blower. It is actuated by a rapid action drive to close quickly when the system is operating in automatic
recirculation air mode (AUC mode). This flap also acts as a dynamic pressure compensator.
Recirculation Air Flap: This flap is a three vane
louver (1).
The recirculation air flap regulates the volume of
recirculated air inducted into the system.
The recirculating air filter is located directly
above it.
Footwell Flap: These flaps (separate for left and
right) control the flow of air to the front and rear
Rear Seating Area Ventilation Flap: These flaps regulate the volume of air flow and the
temperature (air stratification) from the rear ventilation outlets (separate flaps for left and
Defrosting Flaps: These two flaps are coupled together to regulate the air flow against the
windshield. In all adjustment and control functions, these two flaps are controlled from the
driver's side only.
Warm Air/Cold Air Flap: These flaps control the air flow/temperature stratification to the
outlets in the dashboard and B pillars (separate flaps for left and right). Each pair of flaps
(warm air/cold air) regulate the air flow and the temperature at the same time.
Flap Drives/Stepper Motors: All flap drives are designed basically the same, including
the following components:
• Stepper motor
• Plug housing
• Reduction gearing
The external distinguishing features are the different types of levers and rods and the physical
configuration (alignment) of the connectors. The
drives are decured by clips.
IHKA has a total of 11 stepper motors:
• 1 Rapid action motor for the fresh air flap
• 10 Stepper motors for all other flaps
Rapid Action Motor (Fresh Air Flap): The windings of this drive are actuated directly by the
IHKA control module at a stepping frequency up to 500 Hz. The rapid action motor torque
depends on the stepping frequency, not on the supply voltage.
Stepper Motors (All Other Flaps): Each of these motors contain an integrated circuit (MUX4 chip) in the plug connection housing. This IC controls the windings of the motor and is
linked by a motor bus with diagnosis capabilities.
All stepper motor drives are controlled by the IHKA control module over the motor bus.
Each drive has a permanent address (stored on the chip) which is a unique identifier for
the individual motor (for bus communication). The stepper motors are all different and are
not interchangeable.
Faults (blockages) reported by the drives are stored in the IHKA control module, which
responds by discontinuing control signals to the motor in question.
Control Panel/Control Module
The IHKA detailed controls are:
1. AUTO left button (LED: green)
2. Recirculated air/AUC button (LED: both green)
3. DEFROST button (LED: orange)
4. TEMPERATURE left knob
5. MAX AC button (LED: green)
6. AIR VOLUME left knob
7. System OFF button (LED: orange when system is switched off)
8. AIR VOLUME right knob
9. TEMPERATURE right knob
10. REST button - residual heat mode (LED: green)
11. Rear window defroster button (LED: orange)
12. Air Conditioner button (LED: green)
13. AUTO right button (LED: green)
14. Air grill for interior temperature sensor
15. Parked-car ventilation system indicator (flashing when activated)
Function Operations Based on Ignition Switch Positions
Terminal 30 (Ignition OFF)
Terminal 15
• Residual heat (Rest function)
• Parked-car ventilation
• Parked-car ventilation
• AUTO Driver
• AUTO Front passenger
• AC
• Recirculating air
• HHS (rear window defroster)
Terminal R (Accessory Position)
Residual heat (Rest function)
Parked-car ventilation
AUTO (residual heat/parked-car ventilation)
OFF (residual heat/parked-car ventilation are
deactivated when "OFF" is selected)
Communication Between IHKA and Control Display
The following messages are interchanged between the IHKA and the Control Display over
the K-CAN bus:
From IHKA to Control Display:
• Status of air conditioner, front
• Status of air distribution, driver's side
• Status of air distribution, passenger's
From Control
• Operation
• Operation
• Operation
Display to IHKA:
of air conditioner, front
of air distribution, driver's side
of air distribution, passenger's
Functions of Other Buttons on the Control Panel
CENTERLOCK: The status of the CENTERLOCK button is looped through the IHKA to the
appropriate control module.
looped through the IHKA to the appropriate control module. The hazard warning lights indicator LED is activated by the lights switching center.
Connected Loads
The power requirement of the control module is 16 Amp (max.).
Connections at the Back of the Control Panel/Control Module
The rear of the control panel accommodates:
• All plug in connections to the vehicle electrical supply and to the heater/air conditioner
• Connection to the K-CAN bus
• Replaceable sensor blower (directs air onto the integrated interior temperature sensor)
Rear View of the Control Panel:
1. Replaceable sensor blower
2. Pin receptacle 04, 3-pin, black
3. Pin receptacle 03, 12-pin, blue
4. Pin receptacle 01, 12-pin, black
5. Pin receptacle 05, 5-pin, black
6. Pin receptacle 02, 26-pin, blue
M1 to M10 - Flap drives (stepper motors)
BEL AB - Ventilation for storage box (future)
WHZG - Wiper parked zone heating
M11 - Fresh air flap
PM - Power module
WTFL - Heat exchanger temperature
sensor, left
KMV - Refrigerant compressor
WTFR - Heat exchanger temperature
sensor, right
HSR - Rear window roller blind
VDF - Evaporator temperature sensor
KL30 - Terminal 30
F2 - Fresh air grill, front
GEB - Blower
DSEN - Refrigerant pressure sensor
CON - Controller
AUC - Automatic recirculated air control
BZM - Center armrest control console
WV - Water valve
CD - Control Display
ZWP - Auxiliary water pump
DME - (ECM) Digital engine electronics
LM - Light module
ZGM - Central gateway module
WB - Hazard warning lights system
SP - Blocking circuit
CTL - Centerlock
HHS - Rear window defroster
CAS - Car Access System
AT - Antenna tuner
SSEN - Solar sensor
PT-CAN - Powertrain bus
F1 - Fresh air grill, rear seating
K-CAN S - Body controller area network
BSEN - Fogging sensor (future)
Functional Circuit Diagram
Temperature and Air Flow Control
Principle of Operation
Temperature Control
The basis of the temperature control system consists of the left and right master controllers
(Y Factor). These controllers compare the interior temperature actual value with the occupant's requested temperature settings for left and right. The control obtains a differential
signal, which it uses to generate the variable Y (factor).
The operating range of the master control is from - 200% to + 311.5% Y. A wide variety of
functions in the IHKA are influenced by this, for example: the flap and automatic blower
control. The subordinate systems include two auxiliary regulating circuits for the left and
right heat exchangers to suppress the temperature fluctuations in air throughput or water
Two other independent loops control the ventilation temperature for left and right, thus
allowing stratification of the air temperature between the footwell outlets and the ventilation
Passenger Compartment Control (Master Controller)
The passenger compartment controller is proportional (linear). The temperature range that
the vehicle's occupants can select is from approx. 61º F to 90º F (16º C to 32º C).
The step interval is:
• Temperature ºF in increments of 1.0 º F
• Temperature ºC in increments of 0.5 ºC
MAX Heating Function
When the setpoint is 32º C, MAX heating is activated for left and/or right individually. The
interior temperature controller is overridden. The temperature of the heat exchanger is
brought up to the maximum of 90 ºC. The variable Y is set to maximum heating (true
Exception: The water valves will remain closed in the parked-car ventilation mode, so the
MAX heating function is cancelled.
MAX Cooling Function
When the setpoint is 61º F, MAX cooling is activated for left and/or right individually. The interior temperature controller is overridden. The heat exchanger temperature is reduced to the minimum of 5 ºC and the water valve(s) is
closed. The variable Y is set to -200% (maximum cooling) and the recirculation mode automatically takes place.
Correction for Setpoints
Outside Temperature Influence: The outside temperature is registered by a sensor at the
bumper and is sent to the IHKA over the K-CAN bus. The setpoint is corrected to compensate for the effects on the vehicle's occupants from radiant heat. The outside temperature influence and the associated setpoint increase can be between +12 to -2 ºC.
Interior Temperature Sensor: The temperature sensor measures the temperature inside the
passenger compartment. This temperature sensor furnishes the most important, the sensor value is monitored and processed at a very high resolution (0.1667 ºC).
Heat Exchanger Control
The temperature of the heat exchangers is monitored by temperature sensors situated
directly in the discharge air flow (left and right). The heat exchanger setpoint is calculated
on the basis of the master controller's variable Y to correct fluctuations in heat exchanger
Exception: If the variable Y factor is < 0%, the water valve of the heat exchanger(s) is
Heat Exchanger Characteristic Map
The duration of water valve(s) opening compensates temperature control based on a speed
dependent heat exchanger characteristic map for various engine speeds.
Pulse width modulation from the IHKA controls the water valves to open longer for lower
engine rpm and open shorter for higher rpm.
Filling Station Effect
The filling station effect occurs when the valves are de-energized (sprung open), allowing
the heat exchanger to filll with hot coolant. This is avoided by maintaining the power supply to the water valves for 3 minutes after KL15 is switched “OFF”.
Engine Characteristic-Map Cooling
To avoid damage to the heater and air conditioner, the heat exchanger temperature is limited to a maximum of 90 ºC. If a defective water valve causes the temperature in the heat
exchanger to rise too high (> 98 ºC), a K-CAN message is sent to activate the
Characteristic-Map cooling in the ECM.
Auxiliary Water Pump
The electric auxiliary water pump ensures that the requested water flow rate is maintained
even at low engine speeds.
ON: Residual Heat Function
KL15 ON and
Engine temperature > 0 ºC and
Blower not on zero setting and
Variable Y (driver or passenger) > 5%
MAX heating
OFF: Residual heat function not active and
Engine temperature < 0 ºC
Blower setting on zero
Variable Y (driver or passenger) < 0% and
DEFROST not active and
MAX heating not set
Face Vent Outlet Stratification
To achieve the air temperature and air flow rate, output is calculated taking the following
variables into account:
Temperature setting selected by the occupants (variable Y)
Air stratification setting using the Controller in the Control Display settings menu
Ventilation temperature (actual value)
Solar sensor
Outside temperature
Flap characteristics for the footwell
Correction factors
Temperatures of evaporator and heat exchanger
Once the face vent outlet stratification is set, characteristics are applied to correct the positions of the cold air and warm air flaps (air mix) to achieve the desired flow rate and temperature at the ventilation outlet.
The proportions of the warm and cold air flow determines the ventilation temperature. This affects the temperature and the air flow rate in the entire system each
time the angle of a flaps is changed.
1. Face vent outlet duct
2. Air flow to ventilation (ventilation temperature)
3. Cold air flap position
4. Cold air flow (evaporator temperature)
5. Warm air flow (heat exchanger temperature)
6. Warm air flap position
Ventilation Control (Stratification) Front
The inputs used to generate the setting for the face vent temperature are:
Temperature variable (Y)
Stratification using the Controller in the Control Display settings menu
Solar sensor value
Outside temperature
The setpoint calculation for the ventilation temperature is based on the heat exchanger and
evaporator temperatures. The calculation provides the approximated flap angles to produce the ventilation temperature.
There are ventilation sensors (left and right) to monitor the ventilation temperature. These
sensors allow the IHKA to monitor the true ventilation temperature which is compared to
the requested ventilation temperature. The IHKA will “fine tune” the flaps to decrease the
The angle of the footwell flap is taken into account as a factor for the volume of air that is
lost when the footwell flap is open. The variable (Y) function is added to force the warm air
flap open in cooling mode (heat exchanger cold) to increase the air volume flow.
1. Evaporator
2. Heat exchanger
3. Warm air flap
4. Cold air flap
5. Flap for rear seating ventilation
(warm air, cold air and shut off)
Ventilation Control (stratification) Rear
The air stratification flaps for the rear of the passenger compartment (left/right are separate)
discharge perform two functions:
• Shut off the flow of air to the vents (shut off flaps at the vents are closed manually)
• Control the discharge temperature by mixing warm air and cold air (flap 5 above)
The limit position switches at the shut off flaps of the center vent will signal a request to the
IHKA to closed or open the supply flap (flap 5 above).
Air Flow Control
Automatic Blower and Flap Control
When the "AUTO" button (left or right) is pressed or a request is made by using the Control
Display, the automatic blower and flap control is activated (depends on variable Y) and the
"AUTO" LED is illuminated. When the blower control knob is turned, automatic blower control (for that) side is deactivated. Automatic flap control remains active. Pressing the "AUTO"
button again reactivates automatic blower control. The current blower output is displayed
on the Control Display in manual mode only.
Dynamic Pressure Compensation
As vehicle speed increases, the increase in “ram air” is controlled by Dynamic Pressure
Compensation to maintain consistent air flow volume. The ram air is compensated by closing down the fresh air flap to restrict the air intake duct in response to the road speed signal (over K-CAN). To prevent the flap position from being changed continuously in response
to minor changes in road speed (overcompensation), buffering is included in the calculation
for the desired flap position. In the 80 to 180 km/h speed range, the fresh air flap angle is
reduced from 100% to 30%.
Manual Blower Adjustment
Turning the control knob(s) clockwise increases blower output and counter clockwise
decrease output. The knobs do not have limit stops and detente in stages from 1 - 14
(power is increased or decreased one level for each click). Blower output is visualized in the
bar indicator in the Control Display.
Once the maximum or minimum setting is reached, turning the potentiometer further in the same direction
has no additional effect and output
remains at the MAX or MIN setting.
The new blower value is immediately transmitted to the Control Display.
A. Manual blower setting
B. Blower output
C. Potentiometer detent position
D. Blower stage
Automatic Blower Boost
Automatic blower boost is available when the flaps are adjusted
manually or automatically.
A. - Blower output
Y. - FA variable, driver's side
To expedite cooling or heating to counter extreme cabin temperatures, the normal range of
adjustment (Y) is increased to - 200% ... 310%. Automatic blower control only responds to
the driver's side value.
Limitation in Cold and Warm Ranges
When the variable (Y) > 10%,
maximum blower output is limited
as a function of coolant temperature.
This avoids unwanted cold air
drafts until warm air can be produced.
A. Limitation in cold/warm ranges
B. Coolant temperature
C. Maximum blower output
Blower Control Function Based on Electricity Supply
When the power module triggers a consumer shutdown over the K-CAN bus, the following applies:
Blower Output
Priority Level
• 50%
• 100%
Note: The reduction in blower output or shutdown for priority level 1 or 4 does not apply to
the "DEFROST" function.
Blower voltage is reduced in the same ratio as the vehicle voltage from 12.0 V downward.
If the vehicle voltage drops 10%
below 12.0 V, the blower control
voltage and the blower voltage
are also reduced by 10%.
A. Vehicle voltage
B. Blower reduction
Effect of Terminal 50 (Start Signal)
During engine starting, the battery is not subjected to the extra load by the blower current
consumption. As long as "KL50 logically on" remains (starter motor), the blower control
voltage is held at 0V (blower off).
Fault Handling, Terminal 50: A communication defect affecting the "terminal 50 logically
on" bus message will shut down the blower and the duration of the active state (KL50) is
The "Terminal 50 Logically On" Status is overridden When:
• KL50 active for longer than 30 seconds
• Engine speed >500 rpm
• "Engine running" K-bus message is received
The original KL50 status is considered invalid, and although no fault message is in memory the function is "logically off". The blower circuit remains inactive until KL15 is switched
“OFF”. The blower circuit is reactivated by the next KL15 ignition “ON” status.
Air Distribution
Principle of Operation
There are a number of ways to select the air distribution mode:
• Automatic program - selectable by the button on the control panel or the air conditioning menu on the Control Display.
• Prioritized programs - selectable by the buttons on the control panel.
• Manual air distribution programs - selectable by the air conditioning menu on the Control
• INDIVIDUAL settings (no program) - selectable by the DUAL function in the air conditioning menu on the Control Display (future).
The air distribution status is always transmitted to the Control Display for the flap range
from 0% (flap closed) to 100% (flap open).
Flap Positions
The flaps are positioned according to the driver’s side control setting (including Y). The
LHD/RHD ID is needed for this purpose when coding. The flaps and positions that are activated (together) for both sides of the heater and air conditioner unit are: fresh air, recirculating air and Defrost.
Flap Position Priorities
The initial position of each flap is defined in according to the following priorities:
Calibrating run (after connection of the battery)
Parked-car ventilation OR utilization of residual heat (Rest feature)
Position run (when KL15 is switched OFF)
DEFROST program
MAX-AC program
OFF mode (blower zero position)
Cold starting interlock
If one of these functions is active, the nominal positions of the motors are used. If none of
these functions are active, the nominal position is recalculated for each flap, taking into
account the button selected (flap program).
Calibration Run
The stepper motors do not have a “feedback” function to recognize the actual positions,
they always move to a reference position. The reference position is the flap limit positions
0% or 100%.
The flaps always move to a limit position for each "power-on reset" (reconnect battery). This
allows the IHKA to start from the reference to properly position the flaps during normal
operation. A calibrating run can also be initiated by the DISplus.
When at the limit position (0% or 100%), the fresh air flap is subjected to an OVERRUN
(precautionary measure). In OVERRUN, the stepper motor is sent "10 overrun steps" every
20 seconds. The fresh air motor is sent overrun steps in the CLOSED direction (so flap is
sealed correctly) and in the OPEN direction (correction if the flap is frozen closed).
Position Run
When the ignition (KL15) is switched “OFF”, the fresh air/recirculated air flap is moved to
the "fresh air position". This ensures the supply of outside air to the passenger compartment in the event of an IHKA failure.
Manual (Individual) Air Distribution
Manual air distribution is controlled through the
Control Display.
The IHKA provides separate individual air distribution settings to increase /decrease airflow for
the driver's and passenger's side.
Automatic Program
Defrosting flaps
To avoid post start fogging, the defroster flap remains closed for 12 seconds after the
engine is started, before operations return to normal. When the DEFROST function is cancelled, the defroster flap is moved to the new flap position (after a slight delay). When the
AUTO button on the driver's side is pressed, the defroster flaps are opened or closed
according to program variable (Y).
The AUTO button on the passenger's side does not effect the position of the defroster flaps.
A. Variable Y
B. Flap aperture
Footwell Flaps
When the AUTO button on the driver's or passenger's side is
pressed, the footwell flaps are
opened or closed according the
the variable (Y) program.
A. Variable Y
B. Flap angle
Settings for the "INDIVIDUAL" Program
The flaps that can be set individually by the Control Display are:
Driver's Side
Passenger's Side
• Defroster flap
• Virtual flap
• Footwell flap
• Virtual flap
• Footwell flap
When the positions of the flaps on the left side
are changed, the program set for the right side
is deleted.
The individual settings allow the flaps on the left
and right sides to be opened or closed separately in steps of 10%.
The correct flap positions are held and can be
called up with the INDIVIDUAL program.
Special Case: When a special program is active (MAX-AC, DEFROST, etc.) the program
selected beforehand is reselected initially if an individual air distribution setting is selected.
Cold-Starting Interlock
Cold-starting interlock avoids unwanted cold air drafts until warm air can be produced and
is activated with the following conditions:
ON: Variable (Y) DRIVER setting = 100% and
AUTO program selected and
Heat exchanger temp. driver’s side < 30 ºC
Cold-starting interlock is deactivated when any one of the three conditions is not met. The
flap positions for cold-starting interlock depends on the outside temperature. If outside
temperature is < 0 ºC, the defroster flap is OPEN and the footwell flaps CLOSED. The
opposite applies for outside temperatures > 0 ºC.
MAX-AC Function
The MAX-AC function enables the user to select the maximum cooling
power by a single touch of a button on the control panel. The MAX-AC function has the highest priority after the DEFROST function.
All functions including DEFROST are deactivated when the MAX-AC button is pressed and
the air conditioning function is switched on. The air conditioning function will remain active
when the MAX-AC function is terminated.
The MAX-AC function is terminated when any button on the control panel is pressed or a
change made to the settings on the Control Display. The newly selected function becomes
active and the settings selected before the MAX-AC function are reactivated (except
DEFROST). Pressing the MAX-AC button while the MAX-AC function is active also terminates the MAX-AC function.
Special functions in conjunction with the MAX-AC function
• Multi-function steering wheel (MFL) actuation: When the MAX-AC function is active there
is no reaction to the MFL controls.
DEFROST Function
The DEFROST function is a priority function in air distribution. DEFROST is
activated by pressing the DEF button. The DEFROST function is the highest
priority function after the OFF function. When the DEFROST function is activated all the function LEDs go out, with the exception of the rear window
heating LED is active (if selected). The blower can be adjusted while the
DEFROST function is active.
Additional Outside Temperature Influence for DEFROST
TA Outside temperature
A Increase in Kelvin (K)
This adjustment is applied according to the following criteria:
Uncontrolled DEFROST function: Outside temperature < -5 ºC
• The corrected setpoints are increased in accordance with the curve above.
• Heat exchanger temperature is brought up to maximum value.
Controlled DEFROST function: Outside temperature > - 5 ºC
• The corrected setpoints are increased in accordance with a curve above.
• The heat exchanger setpoints are increased to at least 30 ºC.
Reactions to Termination of DEFROST Function
When the DEFROST function is active, only the rear window defroster, A/C functions and
the temperature settings can be changed without switching off the DEFROST function. The
DEFROST function is deactivated by pressing any button (except: temperature control
knob, rear window defroster and REST buttons). When the DEFROST function is terminated by pressing the DEFROST button, the control panel settings (stored in memory) are
A recirculated air function activated prior to DEFROST is deactivated, because recirculation
and automatic A/C mode cannot be activated at the same time. This measure prevents the
windows from fogging when the DEFROST function is switched off and further assisted by
a delayed closure of the defroster flap.
If the system is coded for a hot climate, the recirculated air function is stored in memory
along with the other settings (if selected prior to the DEFROST function).
Solar Sensor Effect
The solar sensor allows the IHKA to compensate for sunlight that affects the temperature
inside the vehicle. The solar sensors have an effect on air conditioning control. An increase
in sunlight produces a shift in the functions listed below. The effect is opposite at night or
when the vehicle enters a tunnel.
The solar sensor consists of two photoresistors (left and right), which register the varying
intensity of the light rays. The sensor signals are interpreted in the solar sensor module and
output to the IHKA control module (voltage range from 0 to 5V).
The effect of the solars sensor separately affect the driver's and passenger's side to influence the following air conditioning components/functions:
• Blower: The blower control curve is shifted (increased air flow compensation)
• Air stratification: The stratification temperature is shifted (increased temperature compensation)
• Flaps: The angle of the virtual flap is corrected (increased airflow/temperature compensation)
Rear Window Defroster (HHS)
Pressing the HHS button activates the rear window defrosting and the function LED illuminates. The system is deactivated by pressing the button for a second time, or automatically
when the defrosting period (10 or 17 minutes) expires. Pressing the button during cyclic
operation starts the post-defrosting phase (5 minutes). The HHS function is independent of
the other button activated functions of IHKA with the exception of the “OFF” function.
Defrosting Phase: After KL15 is switched “ON", the time period to optimize the rear window defrosting is set as follows:
Outside Temperature
> -15 ºC
< -15 ºC
Heating Period (Defrosting Phase)
10 minutes
17 minutes
The function LED remains on for the duration of the heating period.
Cyclic operation: The defrosting phase is followed by cyclic operation with 1/4 power for
30 minutes. This is cancelled by switching KL15 “OFF”.
• 3 seconds ON / 9 seconds OFF.
• The function LED remains OFF during cyclic operation.
Reactivation: If the rear window does not remain clear during cyclic operation, pressing the
button again activates the defroster at full power for another 5 minutes. The function
LED lights up. This post-defrosting phase is followed by cyclic operation.
As of priority level 5 of the K-CAN message, low-voltage cutout by the power module is
possible (protection effect of the power module). The HHS is controlled by the IHKA control module.
Fault handling KL50
The communication defect "KL50 logically on" bus message will shut down the rear window defrosting and the duration of the KL50 active state is monitored. After 30 seconds of
"physically on" this status is considered invalid and no fault message is entered in memory. The function will be "logically off" and the HHS circuit remains inactive.
Rear Window Defrosting - ON/OFF Criteria During Starting
During starting (KL50 active), the rear window defrosting is "OFF". The status of the rear
window defroster is transmitted by the IHKA control module over the K-CAN bus because:
• The power module switches the heated rear window on and off.
• The door modules control the outside mirror heating parallel with activation of the rear
window defrosting.
• The navigation system requires the current flow status of the rear window (effects of the
magnetic field).
Wiper Parked Zone Heating
In order to prevent the wiper blades freezing to the glass at low outside temperatures, the
wiper parked zone heating is activated depending on the outside temperature.
< 3 ºC Wiper parked zone heating ON
> 6 ºC Wiper parked zone heating OFF
Low voltage cutout of the wiper parked zone heating by the power module is possible.
Switching conditions for shutdown are applied as of priority level 5 (K-CAN message).
OFF Function
The OFF Function is activated by pressing the left air volume control knob. The functions
switched OFF (current status is saved) when the button is pressed are:
Function LED in OFF button comes on, all others off
OFF at Control Display
All flaps to 0%
Refrigerant system switched off
Blower off
Auxiliary water pump off
Temperature control switched off
Interior sensor blower continues to run
Sensor value is retained
Water valves receive power to maintain the closed position
Recirculated Air / AUC / Auto Recirculated Air
The RECIRCULATED AIR/AUC button has two functions.
• Changeover from RECIRCULATED AIR to AUC and vice verse
• Switch off RECIRCULATED AIR/AUC function (fresh air mode).
Changeover from fresh air mode to AUC or RECIRCULATED AIR:
Press once
AUC function is activated AUC LED “ON” and RECIRCULATED
Press twice
activated - AUC LED “OFF” and
Press three times
Return to fresh air mode - AUC
both “OFF”
To avoid whistling noises from the IHKA, closure of the fresh air flap is delayed for 0.5 sec.
and the stepper (MUX) motor for the recirculated air flap is activated.
Recirculated Air Mode
The recirculated air function can be used to preserve the air quality inside the cabin in situations of poor outside air, when the vehicle is stopped in traffic, or when driving through
tunnels. The recirculated air function is activated when the RECIRCULATED AIR/AUC button on the control panel is pressed or when AUC detects a recirculated air condition. The
fresh air flap closes within a maximum of 1 second; the recirculated air flap opens in
approximately 4 seconds.
The recirculated air function is not saved before the control module enters sleep mode, the
function is not active following a reset.
Note: When in the recirculated air mode, the air conditioning is not automatically activated.
Automatic Recirculated Air Control (AUC)
The IHKA measures air quality by analyzing the AUC-2 sensor signal. The AUC-2 sensor
provides a PWM signal corresponding to the noxious-gas content. The sensor is provided
5V to activate the heating circuit (approx. 500 - 800 mW).
Each time the vehicle is started, the fresh air position is actuated for 30 seconds to allow
proper sensor heating. Sleep mode does not cancel the AUC function.
Relative humidity inside the car can increase during a recirculated air phase, because the
proportion of fresh air is low. This can cause the windows to fog, therefore recirculation in
the AUC function is limited. The limitation time depends on whether the system is in heating or air conditioning mode:
• Heating mode - The recirculating air time period is limited to 4 minutes at outside temperatures > 6 ºC and is followed by 1 minute of fresh air.
• A/C mode - The recirculating air time period is limited to 12 minutes at outside temperatures > 6 ºC and is followed by 1 minute of fresh air.
Automatic Recirculated Air
This special function rapidly cools the interior of the vehicle. When the occupant requests
maximum cooling power from the air conditioning, cool air from inside the cabin is drawn
back through the evaporator again. This results in a quicker temperature drop inside the
This function initially operates for 12 minutes in the full recirculation air mode and then in
partial recirculation air mode (fresh air 30% / recirculated air 100%). If this function is cancelled within the initial 12 minutes and reactivated, the function operates in the partial recirculation air mode. The automatic recirculated air function is switched ON and OFF according to the following:
A/C mode selected and the
variable (Y) < -20%
A/C mode is terminated
The variable (Y) > -5%
Stationary Functions
Principle of Operation
The IHKA will operate features (when programmed) to enhance cabin comfort based on
exiting heating and air conditioning systems and components. The IHKA Stationary
Functions include: Residual Heat (rest) and Parked-car Ventilation.
Residual Heat
The Residual Heat (rest) function uses the residual engine heat after it is switched off to heat
the passenger compartment. When the REST button is pressed, the Residual Heat function is activated when KL15 is switched “OFF” and KLR is “ON”. The auxiliary water pump
is activated to circulate the hot coolant. The maximum “ON” time is 15 minutes.
The Residual Heat function active when:
REST button is pressed
Outside temperature < 15 ºC
Engine coolant temperature is > 70 ºC
Ignition switch is in position R (KL15 OFF)
15 minutes has not elapsed since KL15 was switched “OFF”
This function is deactivated when KL15 is switched “ON”. When KLR is “ON”, the AUTO
buttons can also be pressed. The AUTO function is cancelled when KLR is switched “OFF”,
but the Residual Heat function will still remain active.
Settings with "Ignition Lock in Position R":
Control panel remains active
Temperature can be controlled
Flap program available
Blower speed adjustable
Function lighting ON
DEFROST, HHS, RECIRCULATED AIR/AUC and MAX-AC functions are not active
Settings with the "Ignition OFF":
Control panel is inactive
• Temperature control is held
• Flap program and blower setting of independent heating are held
• REST function lighting is active
Parked-car Ventilation (SL)
The Parked-car Ventilation blows ambient air into the passenger compartment to lower the
interior temperatures. The air enters the passenger compartment through the vent outlets
in the instrument panel, which can be adjusted for both direction and flow (must be open
for the system to operate). The system remains on for 30 minutes. The system can be
switched on and off manually.
The outside temperature must be > 50 ºC to activate this function. Using the Control
Display, the Parked-car Ventilation function has 2 control options: Direct (manual) operation
and Timer programming.
Activating and Deactivating Manually:
• Ignition in position “KLR”
• Select “Indep. vent.” on the second page of
the “Climate” menu and confirm to activate
• Select “Indep. ventil.” a second time and
confirm to deactivate
Timer Programming (two available times):
• Ignition in position “KLR”
• Select “Indep. vent.” on the second page of
the “Climate” menu and confirm
• Select “Set time1” / “Set time 2” and confirm
• Enter the desired time by turning the Controller and press to confirm
To Activate Timer:
• Select “Switch time 1” / “Switch time 2” and
The Parked-car Ventilation is only available for
activation within the subsequent 24 hours. After
this the time will have to be reconfirmed.
Terminal R “ON” (Control Panel is Active):
Temperature control OFF (water valves closed)
Flap program manually selectable
Blower manually adjustable
Function lighting ON
Function buttons not active
Terminal 15 “OFF” (Control Panel is Inactive):
• Temperature control: OFF (water valves closed)
• Flap program (0% = flap closed / 100% = flap open)
- Warm air left and right 100%
- Recirculating air 0%
- Defrosting 0%
- Footwell left and right 0%
- Cold air left and right 100%
- Rear seating area left and right 0%
- Fresh air 100%
- Blower set to 50%
• Function lighting OFF
Note: The stationary functions are registered with the power module and are subject to
deactivation by the power module (priority lever consumer shutdown > 6). The power module continuously monitors the battery state of charge while the Parked-car Ventilation function is active. When the power module issues the shutdown signal for the independent consumers, the IHKA will shut down the Parked-car Ventilation and it will not be reactivated.
The IHKA will send a CAN message "status air conditioner Parked-car Ventilation" with the
"INDEPENDENT VENTILATION not active" information to the Control Display. The Control
Display responds by updating the on screen display.
Non-Air Conditioning Functions
Rear Window Roller Blind Control
The IHKA controls the roller sun blind for the rear window and provides the OPEN/CLOSED
information to the side window roller sun blinds.
Principle of Operation
The rear window roller blind is controlled by K-CAN messages sent by one of the door
modules. The IHKA distinguishes between short and long actuation of the button.
Short actuation of the button (< 750 ms) will cause the rear window roller blind to be activated. If the button is pressed longer, a request is sent to the door modules to move the
side window roller blinds in the same direction as the rear window roller blind.
When the motor of the rear window roller blind is stopped short, the motor will move in the
opposite direction (OPEN or CLOSE), depending on the previous detected limit position.
The direction of motor rotation is reversed when the button is pressed while the motor is in
operation. The motor continues to receive the drive signal until it stops.
The first time the button is pressed after the engine is started (and KLR active), the motor
will attempt to move the roller blind down, because the current position is not known. If the
motor immediately blocks, the direction of rotation is reversed. To protect the motor, the
drive signal is cancelled after 15 seconds (or current draw exceeds 8 amps).
Actuation and Fault Recognition
The illustration shows the motor of the rear window roller blind.
S - Switches in doors
TM - Door module
CAS - Car Access System
K CAN P - K bus periphery
K CAN S - K bus system
mC - Micro-controller
ECU - IHKA control module
D - Diagnosis output
S1...S4 - Electronic switches
A - Rear window roller blind “OPEN" signal
B - Rear window roller blind “CLOSED" signal
The following faults can be recognized:
• Short circuit to B+ or open circuit: A fault is detected as long as the motor is actuated
and the current is below the threshold. The motor is de-energized.
• Short circuit to ground: A fault is detected when one of the outputs is actuated and the
current is above the threshold. The motor is de-energized.
• Excessive temperature: The internal temperature monitor deactivates the outputs.
• Overvoltage, undervoltage: The outputs are switched off in response to overvoltage or
The following coding information is factored into the IHKA control module:
Vehicle type variants
Engine versions
Specifications for national markets
Special equipment
Control module variants (independent heating, RHD/LHD cars)
The coding data is uploaded to the memory (EEPROM) of the IHKA control module, but is
not active until the control unit has been reset.
Control Module Identification
The data written into the memory chip for control module identification is:
BMW part number
BMW control module version number
BMW coding index
BMW diagnosis index
BMW variant number
Manufacturer's date of production
Manufacturer's catalogue of messages
Manufacturer's software version
Manufacturer's standard core version
Manufacturer's reserve
BMW change index
BMW test stamp
Overview of BMW control module versions:
Version for IHKA Manufacturer
IHKA High without roller sun blind
IHKA High with roller sun blind
Control Module Number
Key Memory
The custom settings of four different radio control keys can be saved in memory (EEPROM)
after KL15 is switched “OFF”. One of these four sets of settings is reactivated when KL15
is re-energized with the corresponding key. The last setting is activated either when the
engine is started with the workshop key or if the information for the key number is incorrect. The information for the key number is sent as a K-CAN message.
Following a reset (KL15), the IHKA sends a message to the CAS requesting what key is
currently in the initialization phase. Driver specific data is stored in memory blocks (EEPROM) for the total of four distinctive radio control keys.
When one of these radio control keys is used, the appropriate memory block is called and
the contained settings are activated. A fifth memory block contains default settings (in case
a valid key is not recognized).
The following data is stored in each of the five memory blocks:
Temperature, left
Air distribution program, left
Air distribution, bottom left
Air distribution, top left
Blower, right
Air stratification, right
Air distribution, middle right
• Blower, left
• Air stratification, left
• Air distribution, middle left
• Temperature, right
• Air distribution program, right
• Air distribution, bottom right
• Air distribution, top right
Active function:
• Always saved: AUC, AC, OFF
• Can be activated by coding:
- Start with AUTO
- Start with AC
- Higher/lower blower characteristic
Vehicle Memory
Vehicle Memory includes all actions permanently saved in the IHKA before the control module enters sleep mode and are reactivated after a reset (KL15).
Saving Control Panel Status
• Terminal 15 ON, engine stopped. Each change to the control panel settings is saved
approximately 1 second later in the control module.
• Terminal 15 ON, engine running. Each change to the control panel settings is saved
approximately 10 seconds later in the control module. DEFROST, MAX AC, RECIRCULATED AIR and HHS are cleared when the consumer is switched off.
Exception: Hot-climate version (can be coded). The RECIRCULATED AIR or MAX AC function, if activated before shutdown, is saved with the other settings.
Coding Variants for Control Panel Functions
• Hot-climate version. When this version is coded the recirculated air function (if active) it
is saved to memory (EEPROM) along with the other data when the control module enters
sleep mode and is immediately available the next time the engine is switched on.
• Off lock. When this version is coded the OFF function is deleted when the control module enters sleep mode, the next time the engine is switched on the functions active
before the OFF button was pressed are automatically reactivated.
• Automatic variants and automatic air stratification. The IHKA offers three variants for
handling the AUTO function. There are also three different modes of setting air stratification to 50% when the AUTO function is switched on.
Custom Settings
The INDIVIDUAL program (EEPROM) can be used to save a data set with the following
user-configurable flap settings for each side:
• Air distribution, head
• Air distribution, chest
• Air distribution, feet
The data sets for the INDIVIDUAL program are saved when the "NO PROGRAM" option is
active and the memory button is pressed. The flap position settings are reactivated as soon
as the user selects the "INDIVIDUAL" setting on the Control Display.
Power Module Influence
The power module uses the CAN message (power management) battery voltage signal
"Control peak-reduction priority" to control consumer shutdown by priority levels. The IHKA
system responds to these priority signals by implementing the following measures:
• Priority 6 measures
- Wiper parked zone heating OFF
- Rear window defrosting OFF (applies to normal operation only, not in cyclic operation)
• Priority 5 measures
- Wiper parked zone heating OFF
- Rear window defrosting OFF (applies to normal operation, not in cyclic operation)
• Priority 4 measures
- Blower set to max. 50%
• Priority 1 measures
- Wiper parked zone heating OFF
- Rear window defrosting OFF (applies to normal operation, not in cyclic operation)
- Blower set to max. 25% (at this time the blower is shut down)
• When the "Status of independent consumers" is received = SHUTDOWN
- Parked-car Ventilation OFF
- Residual heat OFF
Note: The DEFROST function always has 100% blower power available (safety relevant
Sleep / Wait / Power Down Modes
Sleep Mode
To achieve the IHKA control module required standby current consumption (< 100 mA),
network management forces it to enter sleep mode by isolating it from terminal 30.
Wait Mode
Conditions for wait mode:
• The control module run on time must be expired, 2 run on times are possible.
Run on time of the control unit
3 minutes
15 minutes
Terminal 15
Conditions for Residual Heat
not satisfied
• The run on time for the water valves must be expired (fuel station effect can be coded).
The control module enters a wait routine and is de-energized when all run on timers
have timed out.
Individual Sensor Values / Actuator Outputs
Interior temperature sensor
Failsafe value: 20 ºC
Heat exchanger temperature sensor
Failsafe value: 55 ºC
Evaporator temperature sensor
Failsafe value: 2 ºC
Ventilation temperature sensor
Failsafe value: 20 ºC
Pressure sensor
Voltage supply: 5 V ±0.25 V
Output voltage: 0 V...5 V
The pressure sensor outputs a voltage that is linear to the refrigerant pressure (from 0.4 V
to 4.6 V range). The refrigerant compressor is switched off if pressure is excessive.
Solar sensor
Voltage supply: 5 V ±0.2 V
Output voltage: 0 V...5 V
AUC-2 sensor
Voltage supply: 5 V ±0.25 V
Output voltage: 0 V to 5 V
Refrigerant compressor control valve
Resistance of control valve at +20 ºC:
Resistance of control valve at +70 ºC:
10.6 W ±0.5 W
14.5 W ±0.5 W
Auxiliary water pump
Switch on current:
Rated current:
approx. 5.0 A/100 ms
1.5 A
Fresh air flap / rapid action motor
8 ohms ±7% (500 Hz)
Bus stepper motors
100 ohms (200 Hz)
Review Questions
1. List the gasses detected by the AUC-2 sensor.
2. Explain how the refrigerant compressor output is varied.
3. List the refrigerant compressor “Run In” procedure.
4. Where is the blower motor and blower control module located?
5. What are the “Master” function controls on the control panel?
6. Explain the “Y” factor.
7. How is the temperature increased during air conditioning operation?
8. List the functions that apply to heater operation when the coolant is cold.
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