Heating and A/C Functions - II
Heating And A/C Functions
Air distribution
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.
Prioritized programs: Prioritized 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).
Flap settings/flap positions
Non-side-separated flap settings: For the non-side-separated flaps
- Fresh air
- Recirculated air
- Defrosting
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:
- Reference run (after connection of battery)
- Independent heating/ventilation or residual heat utilization
- Position run (with dropping terminal 15)
- DEFROST program
- Max A/C program
- OFF mode (=blower zero position)
- Cold starting interlock
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 module 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
Manual (individual) air distribution is performed from the control display (on-board monitor).
Manual air distribution for Basic version
In the High version, individual air distribution on the driver's and passenger sides can be adjusted separately with the exception of TOP.
Manual air distribution for US programs
In the High version, individual air distribution on the driver's and passenger sides can be adjusted separately.
Automatic program
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's 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:
- Controlled variable Y > 90 % and
- Heat exchanger temperature < desired ventilation temperature + correction value
The opening angle of the virtual flap can be further reduced by means of different blower settings on the driver's and passenger's 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.
Prioritized programs
For the prioritized functions, flap setpoint positions are established which are automatically set. In the programs
- Independent heating
- Independent ventilation
- Residual heat
with terminal R activated, the "normal" flap settings which would be valid during operation without these programs are assumed.
Cold starting interlock
The cold starting interlock is active when the following criteria apply:
- Controlled variable Y (driver) = 100 % and
- AUTO program is selected and
- Heat exchanger temperature (driver) ≤ 30 degrees C
The cold starting interlock is deactivated if one of the condition 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 degrees C, the defrosting flaps are in the OPEN position and the footwell flaps in the CLOSED position. At an outside temperature > 10 degrees C, the defrosting flaps are in the CLOSED position and the footwell flaps in the OPEN position.
MAX A/C function
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
- when any button is pressed in the control panel or
- by a change in the settings in the control display (on-board monitor).
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
- terminal 15 ON (ignition ON) and
- MAX A/C button pressed (ON) and
- outside temperature > 0 degree C.
Active settings: When the MAX A/C button is pressed, the defined settings are approached with an active MAX A/C function.
DEFROST 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.
Solar sensor influence
In the High version, a solar sensor is installed on the instrument panel in the grill 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's sides separately. The following functions are altered:
- Blower (shift of blower envelope)
- Stratification (shift of stratification temperature)
- Flaps (shift of virtual flap angle)
Rear-window defroster (demister)
The rear-window defroster is activated when the HRW button is pressed. Check-back is signaled 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 after heating 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 rear-window defroster is set as follows after terminal 15 ON (restart after sleep mode) during the first switch-on procedure:
- Outside temperature ≥ -15 degrees C: heating time 10 minutes
- Outside temperature ≥ -15 degrees C: heating time 17 minutes
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.
Wiper rest heating
To prevent the wiper blades from freezing solid, wiper rest heating is switched as a function of the outside temperature:
- Outside temperature < 3 degree C: activation of heating
- Outside temperature > 6 degree C: deactivation of heating
OFF function
In the IHKA High version, the OFF function is activated by pressing the left air volume control. This triggers the following functions:
- The current status is saved
- The function LED in the OFF button is activated, all other LEDs are deactivated
- OFF is indicated in the control display (on-board monitor)
- All flaps are closed (0 %)
- The blower is switched off
- The auxiliary water pump is switched off
- The temperature controller is switched off
- The inside sensor fan continues to run
- The sensor value is frozen
- The water valves are supplied with current (heat exchanger is shut off)
When any button is pressed, "IHKA OFF" is canceled and the selected function is activated or deactivated (in the case of the OFF button).
Recirculated air/AUC/automatic recirculated air
The following states can be selected with the RECIRCULATED AIR/AUC button:
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 RECIRCULATED AIR/AUC button in the control panel is pressed or
- AUC detects an ambient condition.
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 module's sleep mode, i.e. the function is canceled after reset.
Automatic recirculated air control (AUC): For measurement of the air quality, two different sensor systems are evaluated by the IHKA:
- AUC I: The sensor system operates with resistance reduction in the event of pollution gases. When the car is started, the system is always switched to the fresh air setting for 90 seconds (sensor heating). EXCEPTION: Car and key memory.
- AUC II: The sensor system operates with the output of a pulse-width-modulated signal in accordance with the pollution gas content. When the car is started, the system is always switched to the fresh air setting for 30 seconds (sensor heating).
The AUC function is not canceled 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).
- In heating operation, the recirculated air time is limited to 3 minutes. After this, fresh air is admitted for 1 minute.
- In A/C operation, the recirculated air time is limited to 12 minutes. After this, fresh air is admitted for 1 minute.
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 canceled 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:
- ON: When A/C operation is selected and the relevant controlled variable (Y-value) is less than -20 %.
- OFF When A/C operation is quit.
- OFF When the relevant controlled variable Y is greater than -5 %.
Encoding
In order to store the vehicle-specific data, the following details must be taken into account:
- Vehicle model variants
- Engine variant
- Country-specific equipment
- Special equipment
- Control module variants (independent heating, RHD/LHD)
The encoding data are transmitted to the control module memory but are only effective after the control module has been reset.
Key memory
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 initialization phase with the aid of the inquiry 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 recognized.
A fifth memory block serves as the standard setting, e.g. in the event that no key is recognized.
The following data is stored in each of the five memory blocks:
- Temperature, left
- Blower, left
- Air distribution program, left
- Stratification, left
- Air distribution, left, bottom
- Air distribution, left, middle
- Air distribution, left, top
- Temperature, right
- Blower, right
- Air distribution program, right
- Stratification, right
- Air distribution, right, bottom
- Air distribution, right, middle
- Air distribution, right, top
- (Status HKA)
- Active function:
- Always stored: AUC, A/C, OFF
- Can be activated by encoding:
- Start with AUTO
- Start with A/C
- Increased/reduced blower curve
Car memory
The car memory includes all the actions which are stored in the IHKA before the control module's sleep mode and are adjusted again after a reset.
Storing control panel status:
- Terminal 15 ON, engine stopped. Each change to the control panel setting is stored in the control module after 1 second.
- Terminal 15 ON, engine running. Each change to the control panel setting is stored in the control module after 10 seconds. DEFROST, MAX A/C, RECIRCULATED AIR and rear-window defroster are canceled after consumer deactivation.
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:
- Umluft_Memory: If this variant is encoded, the RECIRCULATED AIR function is also stored in the control module's sleep mode in relation to the key when it is active. The function is immediately available again the next time the system is switched on.
- OFF_Memory: No car memory function.
- Automatic variants and autostratification: There are three variants available to the IHKA for handling the AUTO function.
- Basis_OFF: An OFF state can also be achieved here for the Basic version. In the minimum blower setting, the blower control must be turned counterclockwise again here.
Safety function
Load deactivation
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:
- Priority 6: rear-window defroster in timed mode (normal operation only)
- Priority 5: rear-window defroster in timed mode (normal operation only)
- Priority 4: rear-window defroster in timed mode, blower at max. half output
- Priority 1: wiper rest heating OFF, rear-window defroster in timed mode, blower at max. half output, auxiliary heating OFF
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/wait/power down modes
Sleep mode: In order to achieve the required closed circuit current consumption, the control module is intentionally switched via the network management into a state of minimum current consumption (< 100 micro Amps). The wait mode must be taken into account here.
Wait mode: The wait mode starts after the following overshoot times have elapsed:
- The overshoot time for the water valves must have elapsed (filling station effect).
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.
Country-specific version