The IHKA integrated automatic heater - A/C system has the following functions:
The IHKA is used to adapt the in-car climate to the individual needs of the passengers. A Basic or a High version of the IHKA is fitted for this purpose. Information is exchanged between the vehicle components and the IHKA via the K-CAN SYSTEM data bus.
As additional special equipment for the High version of the integrated automatic heating / air conditioning system (IHKA), rear air conditioning (FKA) with integrated cooler box can be fitted.
The FKA is connected to the refrigerant circuit of the IHKA via two non-return valves and a pressure and suction line. The non-return valves are located in front of each evaporator and are only fitted if an FKA is fitted. The non-return valves can only be activated by the FKA if the IHKA has been coded to ”FKA is fitted”.
NOTE: Without coding the IHKA to ”FKA is fitted”, the non-return valves are without current and remain closed. In this case, damage is possible.
The IHKA control system informs the Digital Engine Electronics via the K-CAN data bus of the activation status of the compressor. The compressor is activated by the IHKA if no shutdown criterion (e.g. excessive coolant temperature or kickdown mode) prevents such an activation. When the compressor is activated, it is possible to switch between operation with and without an increase in idle speed.
The idle speed is increased at an
The idle speed is not increased at an
The IHKA control unit records the signals of the IHKA components and controls/regulates the heating and air conditioning process. The IHKA control unit causes the heated rear window to be activated and deactivated by the power module. The output stage for the rear roller blind is also incorporated in the IHKA control unit. The IHKA control unit comes in four versions: Basic and High versions with and without rear window roller blind output stage.
The LM light module provides the IHKA with information on the dimming setting and the light status (e.g. low beam activated). The IHKA controls the brightness of the function and locator lights in accordance with this information.
The power module monitors the battery charge state and the open-circuit current consumption of the car. It also activates or deactivates the heated rear window depending on activation by the IHKA. In addition, the boot lid lock is controlled via the power module. Information is received and sent via the K-CAN PERIPHERALS data bus.
The control panel with control electronics is inserted into the instrument panel. The control panel features only the most important control elements. The ”HAZARD WARNING FLASHERS” and ”CENTERLOCK” (central locking) buttons are also accommodated. These button functions are not evaluated by the IHKA control system. The connections are looped through on a hardware basis.
There are different control panels for the Basic and High versions of the IHKA. The control panel of the basic version is not delivered with an OFF function. This function, however, can be coded per Car Memory.
The control display (on-board monitor) is built into the instrument panel. Precision adjustments of the IHKA functions are carried out at the control display.
The IHKA air conditioner is mounted underneath the instrument cluster on the bulkhead in the middle.
The air conditioner is made up of the following components/functional units:
The air conditioner fulfils the following tasks:
NOTE: When the IHKA is operated for the first time, the measures described under ”Compressor” must be carried out.
Blower: The blower is mounted with the blower motor as an assembly in the glovebox area. The blower can be detached from the motor. Because the blower is mounted on the passenger side, there are different versions for LHD and RHD cars.
Controller: The controller is mounted on the blower motor housing. The controller is activated by the control electronics in the control panel of the IHKA via the MUX bus in the same way as the MUX motors and is capable of on-board diagnosis. The diagnosis information is transmitted to the control electronics for evaluation. If on-board diagnosis identifies a fault which would cause components to overheat, the current is reduced or cut off until the fault criterion has been eliminated.
The blower draws in air as a function of the flap setting either
Air can be drawn in through both channels depending on the operating state.
The flaps serve to distribute the air and to mix hot and cold air.
Fresh air flap: The amount of clean air drawn in by the blower is regulated with this flap. The flap is moved by a high-speed drive so that it can be closed in extra-quick time in automatic recirculated air mode (AUC mode). The fresh air flap also serves to compensate ram pressure.
Recirculated air flap: The recirculated air flap is designed as a louvre with three fins. The amount of recirculated air drawn in is regulated with this flap.
Footwell flap: In the Basic version, the footwell flap directs the air flow into the front and rear footwells. In the High version, the front and rear footwells are supplied separately on the left and right.
Rear compartment ventilation flaps: The rear compartment ventilation flaps (separate on left and right) are only fitted in the High version. These flaps serve to adjust the air flow at the rear compartment ventilation outlets and the temperature (rear compartment stratification).
Defrosting flaps: The two linked defrosting flaps serve to regulate the air flow to the windscreen. These flaps are activated jointly in all adjustment and operation functions from the driver's side only.
Hot air/cold air flaps: The hot air/cold air flaps serve to regulate the air flow at the air inlet grilles of the instrument panel and at the B-pillar vents. The temperature is also stratified with these flaps. The combination of the flap pair regulates the air flow and the temperature simultaneously. The functions are separate on the left and right in the High version.
Different stepping motors are used for particular purposes on the flap drives.
High-speed motors: High-speed motors are only used on the fresh air flaps. The windings of these motors are activated by the control electronics with a stepping frequency of up to 500 Hz.
MUX motors: MUX motors are used on all the other flaps. MUX motors are provided with an integrated circuit for controlling the windings. The integrated circuit is bus- and diagnosis-compatible. All MUX drives and the blower control are activated by the control electronics via a common motor bus (MUX bus). Faults reported by the integrated circuits are registered in the control electronics and result in the activation being interrupted.
Each drive is furnished when manufactured with an unalterable address. This facilitates clear differentiation in bus communication. Because of their individual addresses, the motors cannot be exchanged between each other.
The thermal energy generated by compression of the refrigerant gas in the heat exchanger is dissipated by air cooling to the surroundings at the condenser surface. The refrigerant condenses and turns liquid. In order to prevent corrosion damage, any water present in the refrigerant circuit is bound in the integrated drier. The drier insert can be replaced. It incorporates a filter screen to provided protection against particles.
The compressor compresses the refrigerant gas drawn in by the evaporator and forces it to the condenser. It is always in operation when the vehicle engine is running. Infinitely output regulation is possible on account of its design and activation of a regulating valve with pulse-width-modulated signals by the control electronics. For the purpose of load reduction, only the refrigerating output that is directly needed is generated. The control and switching criteria for this purpose are:
Information is exchanged between IHKA and DME via the K-CAN bus.
NOTE: The compressor must be broken in without fail in the following cases:
Compressor breaking-in: To ensure fault-free compressor lubrication, it is necessary to mix the amount of oil added by the manufacturer uniformly with the liquid refrigerant. For this purpose, the compressor must be operated for a specific period at at speed of between 300 and 1500 rpm.
If the engine idle speed exceeds 1500 rpm, the breaking-in procedure is automatically cut off and a message issued. The breaking-in procedure must then be repeated in its entirety.
Specifications: The air conditioning must be set to OFF when the engine is started. Do not switch on the air conditioning before being prompted.
Carry out the following steps:
The auxiliary fan is needed to cool the condenser. On the EURO version of the N62 engine, an electric suction fan is used. The fan characteristic curve coded for this always outputs at least stage 2 when the air conditioning system is activated. The required fan speed depends on the refrigerant pressure and is transferred by the air conditioning system across the CAN bus to the DME.
The pressure sensor in the pressure line between the condenser and the evaporator supplies the control electronics with signals relating to the system pressure.
The expansion valve is attached to the evaporator. It serves to regulate the amount of liquid refrigerant injected into the evaporator. The liquid refrigerant is metered in such a way that only enough refrigerant as can be fully evaporated is admitted into the evaporator.
The evaporator consists of 27 aluminium plates and has a surface of approx. 5 square metres. Temperature control in the evaporator is performed by the control unit. The evaporator temperature controller operates independently from the other control loops with established controlled variables. The cold air emerging from the evaporator is increased to the desired temperature with the aid of the heat exchanger.
A microfilter is located in both of the filter housings for the intake of air. In the Basic version, it is a particle filter while in the High version, it is a combination of particle filter and carbon canister. The carbon canister retains toxic and fouling gases.
The actual interior temperature value and the setpoint interior temperature value are compared by left and right master controllers. The differential signal resulting from the comparison influences the controlled variable (Y-value) for control.
The operating range of the master controller is configured more widely than the operating range of the downstream controllers. The different IHKA functions, such as e.g. automatic flap and blower facility, are dependent on this control range.
Auxiliary control loops for the heat exchanger on the left and right correct disturbance variables. Disturbance variables can be caused by temperature changes as a result of air flow and water flow fluctuations.
The evaporator temperature is set using a separate regulating circuit and is not a disturbance variable for the system.
Two similarly independent control loops regulate the ventilation temperature on the left and right sides. This helps to achieve a stratification between the footwell vents and the ventilation vents.
The effective temperature range is from 16°C to 32°C (approx. 60°F to 90°F). In this temperature range, the temperature can be set in increments of 0.5°C (1.0°F).
MAX HEATING: At a setpoint setting of 32°C, MAX HEATING is activated individually for the left and/or right sides. Interior control is thereby cancelled. The heat exchanger temperature is adjusted up to the maximum temperature of 90°C. The controlled variable Y is set to ”maximum heating”.
EXCEPTION: The MAX HEATING function must be cancelled so that the water valves remain closed during independent ventilation operation.
MAX COOLING: At a setpoint setting of 16°C, MAX COOLING is activated individually for the left and/or right sides. Interior control is thereby cancelled. The heat exchanger temperature is adjusted down to the minimum temperature of 5°C. The controlled variable Y is set to ”maximum cooling”.
DEFROST: During this function, the interior regulation is disabled. On termination of the DEFROST function, in the same way as for the MAX AC function, the temperatue is matched to normal operation. This matching prevents strong cooling following the DEFROST function.
Outside temperature input: The setpoint value is corrected as a function of the outside temperature. The effects of radiation from outside and surrounding surfaces of the passengers are thus compensated. The outside temperature is recorded in the bumper areas by an external temperature sensor and transmitted via the K-CAN bus to the IHKA. The outside temperature input and thus specified value increase can be between +12°C and -2°C. The outdoor temperature input also serves as so-called pre-activation for a possible disturbance variable.
Interior temperature sensor: The control panel accommodates a temperature sensor with inside sensor fan for recording the interior temperature.
Heat exchanger sensors: Heat exchanger sensors are installed on the left and right sides in the air flow of the heater for recording the discharge temperature at the heat exchanger. The opening time of the water valves is derived from the values thus determined. The water valves are activated with pulse-width-modulated signals.
Filling station effect: When the valves are at zero current, the heat exchanger can fill up with water (filling station effect). To avoid this, the water valves continue to be supplied with current for three minutes after the drop in terminal 15.
Engine map cooling: Coolant temperatures of up to 120°C occur due to the use of map cooling in petrol engines. In order to avoid damage to the air conditioner, the heat exchanger temperature is restricted to 90°C. If faulty water valves cause the heat exchanger temperature to exceed 98°C, map cooling is deactivated in the DME via the K-CAN bus.
Auxiliary water pump: An electric auxiliary water pump is installed in order to ensure adequate water flow through the heat exchanger at low engine speeds. Activation takes place
A virtual flap setting (i.e. does not exist in reality) is calculated in order to achieve the temperature and air volume of the total air flow. The following influencing variables are taken into account in the calculation:
The settings of the cold and hot air flaps are corrected with the virtual flap setting calculated from the points listed. The correction is carried out in such a way that the desired air volume and temperature is reached at the air inlet grille through the mixture of hot and cold air.
The settings of the hot and cold air flaps determine the hot and cold air mass flows individually. They thus determine the total mass flow in addition to the ventilation temperature.
In this system, each change in the opening of a flap influences the temperature and the air flow in the overall system. In the correction of the disturbance variables, a distinction must be made between the High and Basic versions. On the basic version, there is only one ventilation temperature sensor. The stratification setting can only be made from the driver's side. The hot and cold air flaps are adjusted with bus-controlled step motors.
In the automatic program, the virtual flap position depends only on the following influencing variables:
The real flap angle is then calculated from:
This function is only available in the High version. The stratification flaps for the rear compartment are separate. The left and right stratification flaps fulfil the following tasks:
The rotational angles of the stratification flaps result in the following influence on the air stream:
Rotational angle |
Influence on the air stream |
|---|---|
0% |
CLOSED |
56% |
Warm |
100% |
Cold |
Automatic blower and flap settings: The automatic blower and flap facility for the relevant side is activated by operating the left or right AUTO button or after an appropriate prompt by the control display. The associated AUTO function LED is activated. An automatic blower facility dependent on the blower control (Y-value) is activated simultaneously.
The automatic blower facility on the relevant side is deactivated when the blower control is actuated. The automatic flap facility remains active.
Pressing the AUTO button returns the system to the automatic blower facility for the relevant side.
The current blower output is only indicated in manual mode in the control display.
The automatic fan control is dependent on the variable (Y) and the signal of the solar sensor.
Automatic blower increase: Automatic blower increase is available with manual flap setting and automatic flap facility.
The normal setting range is extended so that the car interior can be rapidly cooled down or heated up at extreme inside temperatures.
The automatic blower facility is only dependent on the blower control (Y-value) on the driver's side.
Manual blower setting: The blower output is increased by turning the blower control clockwise. The blower output is reduced by turning the blower control counterclockwise. The set blower stage is indicated in the control display by a bar display.
In the High version, the blower can be adjusted with two potentiometers separately for the left and right sides. In the Basic version, this can be performed with a potentiometer on the left side.
The potentiometers do not have stops. Adjustments are made in increments of one stage per notch. The newly set blower value is indicated without delay in the control display. Continuing to turn the potentiometer has no effect once the maximum or minimum setting has been reached.
Ram pressure compensation: As driving speed increases, the air flow at the air inlet ducts increases overproportionally without ram pressure compensation. This effect can be compensated by reducing the air inlet ducts with the fresh air flaps. For this purpose, the opening angle of the fresh air flaps is altered as a function of the driving speed and the blower setting between 100 % and 30 %.
Electrical-system-dependent blower control: If necessary, priority stages for reducing the blower output are transmitted by consumer deactivation of the power module via the K-CAN bus.
Influence of terminal 50: In order to relieve the load on the car battery during the starting sequence, the blower is switched to OFF as long as terminal 50 is ON.
There are different options available for selecting air distribution:
Automatic program: The automatic program can be selected via a button in the control panel and via the A/C menu in the control display.
Prioritised programs: Prioritised programs can be selected via buttons in the control panel.
Manual air distribution programs: Manual air distribution programs can be selected via the A/C menu in the control display (on-board monitor).
Non-side-separated flap settings: For the non-side-separated flaps
the set value of the master controller (Y-value) on the driver's side is applicable. LHD/RHD recognition (encoding) is required for adjusting the functions.
Priorities: The initial setting of each flap is first determined according to the following priorities:
When one of these functions is active, the specified motor positions established for them are assumed.
Reference run: Because none of the stepping motors is provided with actual position detection, they always move relative to one of the flap end positions (reference point).
With each ”Power On Reset” (connection of battery), the flaps are compulsorily moved into an end position. This occurs e.g. when a control unit is replaced or the power supply is cut off during normal operation. The end position is selected in such a way that the subsequent setpoint position can be reached by the shortest route possible.
The reference run can also be initiated by set values of the diagnostic tester.
Position run: When the car is brought to a stop (with dropping terminal 15), the fresh air/recirculated air flap must be moved into the ”fresh air setting”. This ensures that the car interior is supplied with outside air under all circumstances in the event of an IHKA failure.
Manual (individual) air distribution is performed from the control display (on-board monitor).
Program |
Air distribution, windscreen |
Air distribution, middle |
Air distribution, bottom |
TOP |
OPEN |
CLOSED |
CLOSED |
MIDDLE |
CLOSED |
OPEN |
CLOSED |
BOTTOM |
CLOSED |
CLOSED |
OPEN |
OBEN_MITTE |
OPEN |
OPEN |
CLOSED |
OBEN_MITTE_UNTEN |
OPEN |
OPEN |
OPEN |
OBEN_UNTEN |
OPEN |
CLOSED |
OPEN |
MITTE_UNTEN |
CLOSED |
OPEN |
OPEN |
In the High version, individual air distribution on the driver's and passenger sides can be adjusted separately with the exception of TOP.
Program |
Air distribution, windscreen |
Air distribution, middle |
Air distribution, bottom |
HEAT (TOP, BOTTOM) |
OPEN |
CLOSED |
OPEN |
VENT (ventilation) |
CLOSED |
OPEN |
CLOSED |
FLOOR (BOTTOM) |
CLOSED |
CLOSED |
OPEN |
BI_LEVEL (MIDDLE, BOTTOM) |
CLOSED |
OPEN |
OPEN |
In the High version, individual air distribution on the driver's and passenger sides can be adjusted separately.
Defrosting flaps: In order to avoid starting condensation, the defrosting flap remains closed for 12 seconds after engine is started. This is followed by normal operation.
After the DEFROST function, the defrosting flap is moved with a delay into the new flap position.
When the AUTO button is operated on the driver's side, the defrosting flaps are opened or closed in accordance with a curve program. The AUTO button on the passenger side has no effect on the position of the defrosting flaps program.
Virtual flap: When the AUTO button is operated on the driver's/passenger side, the virtual flap is opened or closed individually on the left/right in accordance with a curve program.
The flaps are always closed when the following criteria are satisfied:
The opening angle of the virtual flap can be further reduced by means of different blower settings on the driver's and passenger sides.
The flap with the smaller blower share is throttled. The flap with the larger blower share remains unchanged.
Footwell flaps: When the AUTO button is operated on the driver's/passenger's side, the footwell flaps are opened or closed individually on the left/right in accordance with a curve program.
For the prioritised functions, flap setpoint positions are established which are automatically set. In the programs
with terminal R activated, the ”normal” flap settings which would be valid during operation without these programs are assumed.
The cold starting interlock is active when the following criteria apply:
The cold starting interlock is deactivated if one of the conditions is not fulfilled.
The flap setting for the cold starting interlock is dependent on the outside temperature. The individual functions are established.
At an outside temperature < 10°C, the defrosting flaps are in the OPEN position and the footwell flaps in the CLOSED position. At an outside temperature > 10°C, the defrosting flaps are in the CLOSED position and the footwell flaps in the OPEN position.
The MAX-AC function enables the user to adjust the maximum cooling capacity at the control panel with only one touch of the button.
The MAX A/C function has the highest priority after the DEFROST function.
All functions including DEFROST are deactivated when the MAX A/C button is pressed. The CLIMATE function is activated if it is not already active. The CLIMATE function remains activated even after the MAX A/C function has been quit.
The MAX A/C function is terminated
The selected function becomes active here and the settings selected before the MAX A/C function are resumed (except DEFROST).
The active MAX A/C function is also terminated when the MAX A/C button is pressed.
Summary of switching criteria: The MAX A/C function is ON with
Active settings: When the MAX A/C button is pressed, the defined settings are approached with an active MAX A/C function.
The DEFROST function has a priority function in air distribution and in the control calculation for heating. DEFROST is activated by means of the DEF button.
The DEFROST function has the highest priority after the OFF function. When this function is activated, all the function LEDs are deactivated except for the HRW LED if HRW is active. The DEFROST flap is opened as a function of the controlled variable.
Blower adjustment is possible when the DEFROST function is selected.
In the High version, a solar sensor is installed on the instrument panel in the grille of the central speaker.
The solar sensor records external heat sources (e.g. sun rays) which influence the climate inside the car and affect the well-being of the car occupants.
Climate control without solar sensors is matched to an empirically determined level of solar radiation. The influence of a solar sensor enables the control to be adapted optimally to the real ambient conditions.
The solar sensor records the varying intensity of solar radiation on the left and right sides.
In the event of increased solar radiation, functions which influence the in-car climate are shifted in their direction of control action. The shift is achieved by entering the correction values of the solar sensor in the control system. The shift is reversed accordingly when driving at night or through a tunnel.
The influence of the solar sensor on the control system is assigned to the driver's and passenger sides separately. The following functions are altered:
The heated rear window is activated when the HRW button is pressed. Check-back is signalled by the function light in the button. The HRW function is deactivated when the HRW button is pressed again or after the heating period of 10 or 17 minutes has elapsed. The 5-minute afterheating phase is activated if the HRW button is pressed during timed operation.
The HRW function is not dependent on the other IHKA button functions with the exception of the OFF function.
Deicing phase: In order to achieve an optimum deicing effect, the time period for the heated rear window is set as follows after terminal 15 ON (restart after sleep mode) during the first switch-on procedure:
The function LED is lit during the heating time.
Timing: After the deicing phase, the heating is switched for 30 minutes at 1/4 heat output according to the following cycle:
ON for 3 seconds
OFF for 9 seconds
The function LED is deactivated during the timing.
To prevent the wiper blades from freezing solid, wiper rest heating is switched as a function of the outside temperature:
In the IHKA High version, the OFF function is activated by pressing the left air volume control. This triggers the following functions:
When any button is pressed, ”IHKA OFF” is cancelled and the selected function is activated or deactivated (in the case of the OFF button).
The following states can be selected with the RECIRCULATED AIR/AUC button:
RECIRCULATED AIR/AUC button |
Function |
|---|---|
Pressed 1x |
AUC function activated (AUC LED light and RECIRCULATED AIR LED dark) |
Pressed 2x |
RECIRCULATED AIR function activated (AUC LED dark and RECIRCULATED AIR LED light) |
Pressed 3x |
Back to fresh air mode (AUC and RECIRCULATED AIR LEDs dark) |
RECIRCULATED AIR mode: The RECIRCULATED AIR function can be used to prevent a deterioration in the air quality caused by external air impairment (e.g. waiting at traffic lights, driving through a tunnel, etc.) when the windows and sunroof are closed.
The RECIRCULATED AIR function is activated when
The fresh air flap is closed in max. one second. The recirculated air flap is opened in approx. four seconds.
The refrigerating circuit is not compulsorily cut in.
The RECIRCULATED AIR function is not saved before the control unit's sleep mode, i.e. the function is cancelled after reset.
Automatic recirculated air control (AUC): For measurement of the air quality, two different sensor systems are evaluated by the IHKA:
The AUC function is not cancelled in the case of AUC I and AUC II by sleep mode.
In a recirculated air situation, the relative air humidity inside the car can increase due to the lack of fresh air. This can cause the windows to mist up. To prevent this, the recirculated air state in the AUC function is limited depending on heating or A/C operation (compressor ON).
Automatic recirculated air: This special function serves to cool the car interior rapidly. When extreme cooling capacity is required, in order to cool the car interior more quickly, the already cooler air inside the car is rerouted through the evaporator. This causes the temperature level to drop far more quickly than in normal operation.
The function runs initially for 12 minutes in full recirculated air mode and then always in partial recirculated air mode (fresh air 30 % / recirculated air 100 %). If the function is cancelled within the 12 minutes, the system will only switch into partial recirculated air mode the next time it is activated.
Automatic recirculated air is switched in the case of the following switching criteria:
In order to store the vehicle-specific data, the following details must be taken into account:
The encoding data are transmitted to the control unit memory but are only effective after the control unit has been reset.
The operating settings of four different drivers (four different radio keys) can be stored in the memory after deactivation of terminal 15. These settings are reactivated when terminal 15 is activated with the relevant key.
The last setting is activated on starting up.
The information of the key number is transmitted by means of a K-CAN message with each terminal change and when prompted.
The IHKA inquires of the CAS as to the current key after a reset in the initialisation phase with the aid of the enquiry message.
The four different radio keys can be used to store driver-related data as a connected memory block. This data is called up again after the radio key has been recognised.
A fifth memory block serves as the standard setting, e.g. in the event that no key is recognised.
The following data is stored in each of the five memory blocks:
The car memory includes all the actions which are stored in the IHKA before the control unit's sleep mode and are adjusted again after a reset.
Storing control panel status:
EXCEPTION: In the recirculated air memory version (can be encoded), the RECIRCULATED AIR or MAX A/C function activated previously is stored if necessary.
Encoding variants for control panel functions: The control panel functions can be encoded in accordance with the application:
In the case of a ”control system peak reduction priority” signal from the power module, the consumers have their power output reduced or are shut down by the IHKA control system according to priority:
In the case of a ”stationary consumers status” signal - DEACTIVATION by the power module, the stationary consumers are deactivated by the IHKA control system: independent heating OFF, independent ventilation OFF, residual heat OFF.
The DEFROST function is relevant to safety and always operates at maximum blower output.
Sleep mode: In order to achieve the required closed circuit current consumption, the control unit is intentionally switched via the network management into a state of minimum current consumption (< 100 µA). The wait mode must be taken into account here.
Wait mode: The wait mode starts after the following overshoot times have elapsed:
Overshoot time of control unit |
Terminal 15 |
Conditions for residual heat |
|---|---|---|
3 minutes |
OFF |
are not fulfilled |
15 minutes |
OFF |
are fulfilled |
Power down mode: With the power down command, the vehicle electrical system is placed for the purpose of rapid closed circuit current measurement in a state that it would normally adopt automatically after the overshoot time has elapsed.
The command is given with the DIS Tester. The overshoot time is thus reduced to max. 5 seconds.