05/07/2017 Automatic climate control ECU (IHKA)
Integrated automatic heating/ air conditioning system (IHKA)
System description:
The IHKA is a water-adjusted heating and air conditioning system with left-right separation. In RR4 model the
equipment available are:
• Integrated automatic air conditioning system and heating (IHKA) with control electronics for rear air conditioning. The
IHKA with control electronics for rear air and conditioning is a heating and air conditioning system with 4 zone control. In
addition to the left-right separation for the driver's and front passenger's sides, the control electronics also allow a left right
separation in the rear passenger compartment.
• Integrated automatic air conditioning system and heating (IHKA) with control electronics for rear air conditioning and rear
air conditioner (HKA). The IHKA with control electronics for rear air and conditioning is a heating and air conditioning
system with 4 zone control. The HKA with left-right separation means that the air temperature and supply (only cooling is
possible) in the rear passenger compartment are additionally regulated via the roof air vent.
Operating description IHKA and integrated panel
Control unit and the panel control of the integrated automatic heating / air conditioning system (IHKA) form
combined one component.
With control panel you can set a different temperature for driver's side and passenger's side. In order to keep
temperature desired, the control unit regulates the climate control picking up the sensor signals and continuously
adapts the control variables for blow-out temperature and blower output. To set the seat heating or active seat
ventilation (if fitted) use the buttons in the control panel.
The following image shows the IHKA control unit with integrated control panel. (Image 1)
• 1) Adjustment plate for amount of air on the left air vent;
• 2) Adjustment plate for amount of air on the right air vent;
• 3) Selector wheel for right climate control; I • 4) Seat heating button, right;
• 5) Seat heating button, left;
• 6) Temperature selector wheel for upper body area, right;
• 7) Temperature selector wheel for footwell, right;
• 8) Climate control off button;
• 9) Button for fresh air mode I air re-circulation function;
• 10) Heated rear window button;
• 11 ) Defrost button;
• 12) Temperature selector wheel for footwell, left;
• 13) Temperature selector wheel for upper body area, left;
• 14) Selector wheel for left climate control;
• 15) Opening for force-ventilated interior temperature sensor;
Control electronics for rear air conditioning with integrated control panel
The control panel and control electronics for rear air conditioning form in one component. They are both installed on
the rear side of the center console.
With control panel you can set a different temperature for driver's side and passenger's side. In order to keep
temperature desired, the control unit regulates the climate control picking up the sensor signals and continuously
adapts the control variables for blow-out temperature and blower output. To set the seat heating or active seat
ventilation (if fitted) use the buttons in the control panel. LIN bus connects the control electronics for the rear air
conditioning with IHKA control unit.
The following image shows the IHKA control unit in the rear passenger zone. (Image 2)
• 1) Adjustment plate for amount of air on the left air vent;
• 2) Adjustment plate for amount of air on the right air vent;
• 3) Selector wheel for climate control;
• 4) Seat heating button, right;
• 5) Temperature selector wheel for upper body area, right;
• 6) Temperature selector wheel for footwell, right:
• 7) Opening for force-ventilated interior temperature sensor; I
• 8) Temperature selector wheel for footwell, left;
• 9) Temperature selector wheel for upper body area left;
• 10) Seat heating button, left;
HKA control unit and control panel
The HKA control unit activates:
• Mixing flap drivers;
• The air distribution flap motors;
• The light-emitting diodes;
• The blower of the rear air conditioner of output stage;
The HKA has 2 different control panels for left-right separation for rear zone. Each control panel is installed near the
roof air vent. They will regulate the air supply and air temperature (only cooling is possible) in the rear passenger
compartment via two roof air vents.The left hand control panel is connected directly via a connection plug to the
right hand control panel. This means that all the settings for the left hand control panel are picked up and digitized
in the electronics of the right hand control panel. Then the right hand control panel sends the signals via LIN bus to
the rear air conditioner control unit.
Blower with blower output stage
The blower consists of:
• Blower motor;
• Fan wheel;
• Blower output stage;
• Housing;
Blower with blower output stage
The blower creates an air mass flow in the heating and air conditioning system. The nominal voltage of the blower
output stage for the blower motor is specified by the control unit of the IHKA, with a message via the UN bus. The
activation of the blower motor via the blower output stage depends on the control signal. (Image 3)
• 1 ) Blower motor;
• 2) Blower regulator
• 3) Blower of the heating and air conditioning system;
• 4) Plug connection ( connection to blower motor);
• 5) Plug connection (connection to the wiring harness);
• 6) Wiring blower;
Rear compartment blower with output stage for the rear compartment blower motor
The rear compartment blower is installed in the center console. The blower creates an air mass flow in the heating
and air conditioning system.The control electronics for the rear air conditioning indicate the nominal voltage for the
blower motor in the rear compartment, to the output stage. The control electronics issue the nominal voltage as a
PWM signal (pulse width modulated signal) to the output stage. The activation of the blower motor via the blower
output stage depends on the control signal. (Image 4)
• 1) Fan wheels;
• 2) Rear compartment blower motor;
• 3) Housing;
• 4) Plug connection;
• 5) Output stage for rear compartment blower motor;
Blower with blower output stage (rear air conditioner)
The blower function is to create necessary air mass flow in the rear air conditioner. The nominal voltage for the
blower output stage for the blower motor is specified by the rear air conditioner control unit, as a message via the
LIN bus. The activation of the blower motor via the blower output stage depends on the control signal. (Image 5)
• 1) Fan wheel;
• 2) Blower motor;
• 3) Motor bracket;
• 4) Rear air conditioner;
• 5) Plug connection (connection to blower motor);
• 6) Blower output stage;
• 7) Plug connection (connection to the wiring harness);
Ionizer
The ionizer contains a ceramic plate covered with toughened glass. An AC voltage of approx 3kV is applied to the
electrode. This device internal high voltage leads to partial ionization of the air from the evaporator. This reaction
generates hydrogen peroxide that remove bacteria from the most part of the evaporator and other components of
the automatic air conditioning system. The IHKA control unit activates the ionizer with a pulse-width modulated
signal (PWM signal). (Image 6)
• 1) Three - pin plug connection;
• 2) Housing;
• 3) Ionizer;
Electric auxiliary heater, rear left passenger compartment, and electric auxiliary heater, rear right
passenger compartment
An electric auxiliary heater is a control electronics for the rear air conditioning, and is installed in every footwell
ventilation duct. A percentage of the power request for the electric auxiliary heater is generated by the control
electronics, that percentage depends on a different signal (e.g. temperature signal from the rear cabin footwell
temperature sensor). The request is transferred via a pulse width modulated signal to the electric auxiliary heater.
The electric auxiliary heater heats the passengers compartment especially at low temperatures or when the vehicle
is just started. It works like an electric radiator. The elements in the electric auxiliary heater are PTC resistors, and
they are made up of individual ceramic semiconductor resistors.
The electric auxiliary heater starts with an high levels of current flows, and as the heating grows, this level of current
falls. These electrical characteristics of the resistors enable a temperature approx. of 120°c in the area surrounding
the heating elements and there is no problem for them. This "physical" overheat protection is ensured, even in the
event of blower failure. (Image 7)
• 1) Footwell temperature sensor;
• 2) Electric auxiliary heater rear left;
Flap motors
The flap motors are activated and powered with voltage and ground across the LIN bus by the corresponding
control unit (IHKA or HKA). In the rest state there is no supply of voltage. The flap motor is fitted with an integrated
circuit that controls the coil of the flap motor. This circuit has diagnosis capabilities and bus. When the flap motor is
activated, the integrated circuit sends a position feedback to the control unit across the LIN bus. Each flap motor is
assigned a certain address, this address determines the choice of which function the flap motor assumes in the
system network. For example, the footwell flap motor in the rear right passenger compartment uses this address to
detect that messages are addressed to it (e.g. open flap). This address tells the IHKA control unit which flap motor
has sent a fault message to it.
Stratification control wheel
The selected potentiometer setting is implemented on the flap position of each flap motor.
Limit-position switch
The limit position switch helps the ventilation flap to pick one of the following positions:
• Ventilation flap open (contact in the limit position switch closed);
• Ventilation flap closed (contact in the limit position switch open);
Eccentric washers switch on or off the limit position switch. The IHKA control unit evaluates the information from the
limit position switch, if the ventilation flap is closed manually, the IHKA activates the corresponding ventilation flap
motor. This setting locks the air flow to the air vents in the ventilation grille.
Sensors
Sensors installed in heating and air conditioning system:
Interior temperature sensor:
• The IHKA front control integrates a force ventilated interior temperature sensor with an interior temperature sensor
blower. The air temperature in the passenger compartment is measured from this sensor by the integrated interior
temperature sensor blower. This works also in the rear passenger compartment;
Refrigerant pressure sensor:
• Between the line of the capacitor and the evaporator is located the refrigerant pressure sensor. The IHKA control units
regulates the air condition compressor in order to prevent an excessive refrigerant pressure. The refrigerant pressure
unit takes its power supply by the power distribution box in the junction box. The data is evaluated in the junction box
electronics (JBE). The prepared data is sent across the body CAN (K -CAN) to the IHKA control unit.
Evaporator temperature sensor:
• This sensor picks up the outlet temperature of the cooled air at the evaporator to avoid icing of the evaporator. This
sensor is directly connected to IHKA control unit. The evaporator temperature sensor of the rear compartment is directly
connected to the automatic rear air-conditioning system control unit.
Rain- light-solar-condensation sensor:
• The solar sensor them allows the IHKA to get the value of solar irradiation, and measures the sunlight on the vehicle.
Sunlight levels are detected in separated ways in driver's side and passenger's side. The condensation sensor detects
the level of condensation on windows and avoids the condensation of them at an early stage without driver intervention.
This sensor provides a series of information like temperature on the inside of the windscreen and the air humidity on the
inside of the windscreen. The sensor data is processed in the evaluation unit of the rain-light-solar-condensation sensor
via the LIN bus. The junction box electronics (JBE) adopts the signals into the corresponding CAN message and sends
them. The IHKA control unit is a bus user on the K- CAN. If some faults comes, a fault entry is made in the junction box
electronics (JBE).
Sensor for automatic air re-circulation mode:
• The AUC sensor is a metal oxide sensor, and this sensor is very sensitive to smells and pollutants. The AUC is located in
the mirco filter compartment. The automatic air re-circulation control sensor evaluates the levels of carbon monoxide and
nitrogen oxides in the air and detects the air quality. The level of air quality will be transformed into an electrical signal,
and there are 10 stages of "air quality", stages 0 to 10 (clean to severely contaminated). Once get the quality air level,
the automatic air re-circulation control transmits it via the LIN bus to the junction box electronics (JBE). This junction
transmits the digital signal via the CAN bus to the IHKA control unit. If the automatic air re-circulation control sensor
measures an emission value that is too high, an automatic changeover recirculated air operation takes place via the I
IHKA control unit.
Heat exchanger sensor:
• Two different sensors are installed into the IHKA, as the blow-out temperature at the heat exchanger for the heating
system is registered separately for the driver's and passenger's side. The sensors are directly connected to the IHKA
control unit.
Ventilation temperature sensor:
• There are 4 ventilation temperature sensors installed. Two of them are installed in the IHKA, as the blow-out temperature
at the middle ventilation flap is registered separately for the driver's and passenger's side. These sensors are connected
to the IHKA control unit. The IHKA control unit regulates the corresponding flap motor by this message. The other 2
sensors are installed with the control electronics for the rear air conditioning in the rear air outlet of the center console
(on the right and left rear air outlet). They are connected to the control electronics for the rear air conditioning, this one
controls the signals sent by the sensors. These signals are sent as a message via the LIN bus and the IHKA control unit
uses this message to regulate the corresponding flap motor.
Rear-cabin footwell-temperature sensor:
• Like the ventilation temperature sensor, two sensors are installed. One of them is attached to each of the left and right
footwell air outlets. The sensors are directly connected to the control electronics for the rear air conditioning. The control
electronics for the rear air conditioning analyses the signals from the rear seat air temperature sensors. Control
electronics for the rear air conditioning evaluates the signals from the sensors, via the LIN bus as message. The IHKA
control unit uses this message to regulate the corresponding rear footwell flap motor.
Roof air vent temperature sensor:
• There are two roof air vents installed in conjunction with the rear air conditioner. The left-right separation sets that a roof
air vent temperature sensor is installed in each roof air vent. The signals of these two sensors are evaluates and digitized
in the control panel of the rear air conditioner on the right. The control panel transmits this signal via LIN bus to the rear
air conditioner control unit. The HKA control unit picks up this information and will activate the air distribution flap motors
and mixing flap drivers.
Dual water valve
The dual water valve is an electromagnetic valve that regulates the coolant flow rate to the heat exchanger. This
sets also the air temperature used for heating the passenger compartment. The dual water valve is controlled by
the junction box electronics (J BE).
Refrigerant shutoff valve at front and rear
The rear air conditioner is connected to the refrigerant circuit of the IHKA. Two different refrigerant shutoff valves
separate the two refrigerant circuits, these refrigerant shutoff valves (front and rear) are only fitted together with the
HKA. Each refrigerant shutoff valve (front or rear) is integrated in the expansion valve of the IHKA or HKA (IHKA for
the front, HKA for the rear) and it blocks the pressure line to the corresponding evaporator. The HKA and IHKA
refrigerant circuits can both work together on in independent way. However, at least one refrigerant shutoff valve
must always be opened. The HKA control unit activates the refrigerant shutoff valves, with no energy no refrigerant
shutoff valves will work.
Air conditioning compressor
The refrigerant taken from the evaporator will be compressed by the air conditioning compressor, pressed towards
the capacitor. The air conditioning compressor is switched on and off by a magnetic coupling. The air conditioning
compressor allows a step less power control, the electric control valve on the A/C compressor influences the
balance of forces by the piston stroke. The junction box electronics (JBE) controls with a clocked voltage the control
valve and the IHKA control unit regulates the activation. For the purpose of load reduction, only the cooling power I
that is closely needed is generated.
Capacitor with integrated dryer flask
During the service, all the gaseous refrigerant in the capacitor will be converted into liquid refrigerant. Any water
present in the refrigerant circuit will be put in the integrated downstream dryer flask.
Expansion valve
The expansion valve sets the refrigerant injection rate into the evaporator, at maximum rate that the evaporator limit
can completely evaporate. Any drops of liquid that have not been evaporated may cause damage in the A/C
compressor.
GENERAL NOTES
Running in A/C compressor:
• If you need to replace the air conditioning compressor or refill the refrigerant circuit, the air conditioning compressor must
be run up. To perform the run up, the air conditioning compressor must work within a specified engine speed range. The
running up procedure will automatically abort if the engine speed exceeds the specified speed range. The running up
procedure must be repeated in its entirety.
Encoding the rain-light-solar-condensation sensor:
• You must encode the rain-light-solar-condensation sensor after a replacement of the windscreen, or a replacement of
sensor self-same.
Encoding of the heating and air conditioning system:
• When you need to encode the vehicle specific data, you need to remember these details and take them into account:
• Engine version;
• Version of the equipment heating and air conditioning system;
• For example, if you install a rear air conditioner, the integrated automatic heating / air conditioning system must be
encoded to "rear air conditioner is fitted" (IHKA control unit will be the master controller, the rear air conditioner control
unit the slave). If you don't encode , the built-in refrigerant shutoff valves (front and rear) remain closed and they will not
function.
WARNING: The makes and distinguishing signs of the vehicle manufacturers included in this document are only provided to inform the reader about the potential suitability of the said TEXA products to be used for the vehicles of the above-mentioned manufacturers. References to makes and models contained in this document are to be considered only as a rough guide.
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