Heating and Air Conditioning - Service Techniques BMW M3 E90

Scheme 111

System functions

The IHR/IHKR/IHKA comprises the following functions

1. Temperature control
2. Evaporator control (IHKR/IHKA only)
3. Air distribution setting
4. Airflow control
5. Sunlight compensation (solar sensor)
6. MAX cooling (IHKA only)
7. Residual heat (IHKA only)
8. Defrost function (IHKA only)
9. AUTO function (IHKA only)
10. Heated rear window
11. OFF
12. Air recirculation mode
13. Automatic air-recirculation control (IHKA only)
14. Program for preventing condensation on the window surfaces (IHKA only)
15. Central kinematics actuation (IHR, IHKR only)
16. Convertible program (E93 only)
17. Independent heater (option 536)
18. Automatic rear air conditioning (option 4NB, E70 only)
19. Additional heating/ventilation for 3rd row of seats (option 4NC, E70 only)
20. Seat heating and active seat ventilation (E70 only)
21. Steering wheel heating
22. Electric steering column adjustment

Temperature control

1. E81, E82, E87, E90, E91, E92, E93: Heating and air-conditioning system controlled on the air side The temperature for the best possible interior climate is regulated with a mixer flap in the heater/air conditioner. The air-mass flow is fed through the evaporator (IHKR, IHKA only). As this happens, the air-mass flow is cooled and dried (providing the air-conditioning system is switched on). The mixer flap then feeds the air-mass flow completely or in part over the heating system heat exchanger and the electric auxiliary heater (depending on the desired temperature value set at the IHR/IHKR/IHKA control panel). The air flows are subsequently mixed again. The air-mass flow is then fed through the ventilation flaps and into the vehicle interior. On the IHKA, the air ducts for the driver and front-passenger are separate. Due to the separate settings for the left and right sides for the driver and front passenger there are 2 mixing flaps. IHR, IHKR Temperature control is based on the nominal value set and a calculated actual value (The nominal value is set at the temperature selector wheel on the IHR/IHKR control panel. The actual value is calculated from the temperatures measured by the ventilation temperature sensor and the footwell temperature sensor.) With the IHR, temperature control below the ambient temperature is not possible. IHKA Control is based on the nominal values set and the calculated actual value (The nominal values are set using 2 temperature selector wheels on the IHKA control panel (separate settings for left and right sides). The actual value is calculated from the temperatures measured by the interior temperature sensor and the footwell temperature sensor). The lead parameter is calculated from the comparison between the actual value for the interior temperature and the corrected nominal value (calculated from temperature request and ambient temperature). Compared to the set specification, the interior temperature is raised in the cold so that a comfortable level is achieved even at negative temperatures, despite the temperature setting being unchanged. The ambient temperature is transmitted to the IHKA control unit via the body CAN (body Controller Area Network).
2. E70: Heating and air-conditioning system controlled on the water side Within the heating/air-conditioning systems, the air-mass flow is first fed through the evaporator. As this happens, the air-mass flow is cooled and dried (providing the air-conditioning system is switched on). The airmass flow is then fed over the heating system heat exchanger and the electric auxiliary heater, where it is heated up to the required nominal value (depending on the desired temperature value set at the IHKA control panel). The air-mass flow is then fed through the ventilation flaps and into the vehicle interior. The IHKA High has separate air ducts for the driver and front passenger. The separate settings for the driver and front-passenger side means that the heating system heat exchanger also has separate settings for the left and right sides. IHKA Basic The temperature in the heating system heat exchanger is controlled with the help of the heating system heat exchanger sensor and a pulsed water valve in the heater circuit. The water valve is actuated with a pulse modulated signal (PWM signal) by the IHKA control unit. A map for the heating system heat exchanger determines the opening times for the water valve, depending on the engine speed. Regulation is based on the nominal value set by the vehicle occupants at the temperature selector wheel and the calculated actual value. (nominal values are set via a temperature selector wheel on the IHKA control panel. The actual value is calculated from the temperatures measured by the interior temperature sensor and the heating system heat exchanger sensor). The lead parameter is calculated from the comparison between the actual value for the interior temperature and the corrected nominal value (calculated from temperature request and ambient temperature). Compared to the set specification, the interior temperature is raised in the cold so that a comfortable level is achieved even at negative temperatures, despite the temperature setting being unchanged. The ambient temperature is transmitted to the IHKA control unit via the body CAN (body Controller Area Network). IHKA High The separate temperature setting for the drivers side and the front-passenger side affects: Heating system heat exchanger with left/right separation 2 heating system heat exchanger sensors 2 ventilation temperature sensors Dual water valve

Evaporator control (IHKR, IHKA only)

The evaporator temperature is regulated by means of the evaporator temperature sensor and the expansion valve. The evaporator temperature is set to the predefined specification of 2 °C. Lower temperatures are not possible due to the risk of icing.

If the "variable evaporator control" function has been encoded, the nominal evaporator temperature is calculated between 2 and 7 °C. The specification depends on the ambient temperature, the ventilation temperature and the refrigerant pressure. A variable evaporator control reduces dehumidification. This reduces the risk of mucous membranes drying out.

Air distribution setting

For the best possible operation of the air distribution, it is important for the manually adjustable air vents to be open.

1. IHR, IHKR Air distribution selection is only possible manually with the air-distribution control wheel.
2. IHKA Occupants have the possibility of allowing the air distribution to be decided by the automatic program (AUTO button). Alternatively, individual, personal settings are possible through manual selection (defrost, ventilation, footwell). If the relevant equipment is fitted to the vehicle, it is also possible to make a fine adjustment via the CID (Central Information Display) in the submenu Air distribution. Compared to manual selection, fine adjustment offers the additional possibility of further individualization of the air distribution. E70: IHKA Basic With the IHKA Basic, the air distribution can only be set manually with the controller. The menu provides the following settings: 4 different presettings and one individually configured setting The vehicle occupants can effect individual air distribution/stratification of hot and cold air inside the vehicle at the same temperature setting. E70: IHKA High In addition, air distribution can also be set at the IHKA control panel. The menu provides the following settings: Driver's side: 4 different presettings and one individually configured setting Passenger side: 3 different presettings and one individually configured setting Settings for ventilation temperature (temperature stratification) can also be made in this menu. With the IHKA High, separate stratification can be set for the left and right sides in the front. Stratification is also possible in the rear. E70: IHKA High with automatic rear air conditioning With the IHKA High with automatic rear air conditioning, stratification can be set separately for the left and right sides in the rear.

Airflow control

The airflow control is dependent on the following settings and control actions

1. Manual blower setting
2. Automatic blower and flap setting (IHKA only) The automatic blower and flap functions are activated when the AUTO button is pressed.
3. Dynamic pressure compensation The air volume at the air inlet grilles increases disproportionately with increasing road speed. This effect is compensated for by the opening angle of the fresh-air flap being reduced as speed increases (dynamic pressure compensation). The opening angle is regulated according to a defined map.
4. Blower control If necessary, the power management system will assign priority levels to reduce the blower output (via K-CAN).
5. Effect of terminal 50 When the engine is being started (terminal 50 ON), the electric auxiliary heater and blower are switched OFF to reduce the load on the car battery.

Sunlight compensation (solar sensor)

1. E70 IHKA High and E81, E82, E87, E90, E91, E92, E93 IHKA

The following functions are modified when automatic mode is activated (depending on the intensity of sunlight)

1. Blower output is increased or reduced
2. Desired temperature value is increased or reduced

1. E70 High

The influence on IHKA regulation by the solar sensor is assigned separately to the driver's side and to the front passenger side.

1. E81, E82, E87, E90, E91, E92, E93 IHKA

How the solar sensor affects the IHKA regulation on the driver's side and on the front-passenger side is not programmed separately.

MAX cooling (IHKA only)

The MAX button makes it possible for the user to select maximum cooling with just one press of a button at the IHKA controls.

When the MAX button is pressed, all functions, including the defrost function, are deactivated. The air-conditioning function is activated (if it was not already activated) and defined settings are selected (e.g. temperature control is deactivated, ventilation flaps are fully opened).

Residual heat (IHKA only)

The residual-heat function allows the waste heat from the engine to be used to heat up the vehicle interior when the engine is not running (e.g. during a stop at a level crossing). The residual-heat function is only possible for a certain run-down period (15 minutes from terminal 15 OFF). The auxiliary water pump is activated to circulate the water.

Switch-on conditions

1. Terminal 15 OFF and
2. Run-down period active (up to 15 minutes after terminal 15 OFF) and
3. REST button* in IHKA controls ON and
4. Ambient temperature below 25 °C and
5. Engine temperature at some point above 60 °C and
6. On-board supply voltage over 11.4 volts

Condition for switching off

1. Terminal 15 ON or
2. Residual heat ON (15 minutes) expired or
3. REST button* in IHKA control panel OFF or
4. OFF condition activated with residual heat active (terminal R) or
5. Prompt from power management to switch off auxiliary consumers or
6. On-board supply voltage less than 11 volts

* On the E70, there is no REST button (residual heat button). The function of the REST button is integrated into the blower speed button.

Defrost function (IHKA only)

When the defrost function is activated, the defroster flap (on the inside in front of the windscreen) is opened fully. The fresh-air/air-recirculation flaps move to the fresh air position. All other flaps are closed. The blower is run up to maximum output.

1. E70 with automatic rear air conditioning

The blower in the rear is switched off.

AUTO function (IHKA only)

When this button is pressed, all IHKA functions are set to automatic mode. If one or more automatically controlled functions are manually set, automatic control for the functions concerned will be cancelled. All other functions remain automatically controlled.

Heated rear window

The heated rear window is switched on when the button in the IHR/IHKR/IHKA control panel is pressed. The function indicator lamp in the button lights up.

The heated rear window is switched off by pressing the button again or automatically after the heating time has expired.

1. E81, E82, E87

1. Defrosting phase (1st heating period) When terminal 15 is switched ON, the first time the system is switched on, the time span for the heated rear window is defined as follows: Ambient temperature down to -15 °C: heating period: 20 minutes Ambient temperature below 15 °C: heating period: 30 minutes
2. Pulsing After the defrosting phase, the heating phase (30 minutes with pulsed heat output (on-off cycle: 40 seconds ON, 80 seconds OFF). The function indicator lamp in the button is off during pulsing.
3. 2nd heating period After the 1st heating period has expired, each subsequent time the button is pressed will cause the heated rear window to be switched on for a further 30 minutes (defrosting phase). After the 2nd heating period has expired, output is again pulsed.

1. E70, E90, E91, E92, E93

1. Defrosting phase (1st heating period) When terminal 15 is switched ON, the first time the system is switched on, the time span for the heated rear window is defined as follows: Ambient temperature down to -15 °C: heating period: 10 minutes Ambient temperature below 15 °C: heating period: 17 minutes
2. Pulsing After the defrosting phase, the heating phase (25 minutes with pulsed heat output (on-off cycle: 40 seconds ON, 80 seconds OFF). The function indicator lamp in the button is off during pulsing.
3. 2nd heating period After the 1st heating period has expired, each subsequent time the button is pressed will cause the heated rear window to be switched on for a further 30 minutes (defrosting phase). After the 2nd heating period has expired, output is again pulsed.

OFF

The IHR/IHKR/IHKA control panel is switched off when the blower speed is set to 0 (The control panel/control unit continues to run in the background.)

Air-recirculation mode

In recirculated-air mode, the flow of outside air can be stopped to prevent pollution from entering the vehicle, e.g. in traffic congestion. Air inside the vehicle is continually recirculated.

To make sure that there is a sufficient supply of fresh air, air-recirculation mode is only available for a limited time (30 minutes air recirculation -> 30 seconds partial fresh air -> 30 minutes air recirculation -> etc.)

Automatic air recirculation control

1. E81, E82, E87, E90, E91, E92, E93 only IHKA
2. E70: IHKA High only

If the AUC sensor detects an increased level of pollutants in the environment from spark-ignition and diesel engines, the IHKA control unit will automatically switch to air-recirculation mode.

To make sure there is still an adequate supply of fresh air, air recirculation is only available for a limited time

1. At ambient temperatures less than 0 °C: 2 minute recirculated air mode -> 1 minute fresh air mode (from 03/2005: 20 seconds) -> 2 minute recirculated air mode -> etc.
2. At ambient temperatures from 0 °C to 6 °C: 3 minutes air recirculation mode -> 1 minute fresh air mode (from 03/2005: 20 seconds) -> 3 minutes air recirculation mode -> etc.
3. Operation without air-conditioning function at ambient temperatures greater than 6 °C: 4 minutes air recirculation mode -> 1 minute fresh air mode (from 03/2005: 20 seconds) -> 4 minutes air recirculation mode -> etc.
4. Operation with air-conditioning function at ambient temperatures greater than 6 °C: 12 minutes air recirculation mode -> 1 minute fresh air mode (from 03/2005: 20 seconds) -> 12 minutes air recirculation mode -> etc.

When the engine is started and the AUC function activated, fresh-air mode is always selected for approx. 40 seconds due to the warming phase of the AUC sensor.

Program for preventing condensation on the window surfaces (IHKA only)

The following conditions must be satisfied for measures against condensation on the windscreen to be effected

1. Engine running and
2. The IHKA must be in automatic mode

The IHKA control unit evaluates condensation sensor signal (humidity). If condensation on the windscreen is imminent, the following measures are initiated in sequence to prevent condensation from forming.

If a measure proves to be ineffective, the next measure is initiated.

Once successful, the measures previously performed are reversed step-by-step in reverse order.

Measures if the windscreen threatens to mist over

1. Open defrost flaps further
2. Switch from air recirculation/AUC/automatic air-recirculation mode to partial fresh-air mode
3. Switch from partially fresh air in air-recirculation/AUC/automatic air-recirculation mode to fresh air
4. Increase air volume with the blower
5. Reduce air volume for the footwell
6. Increase desired temperature value

Central kinematics actuation (IHR, IHKR only)

The air distribution flap motor has the task of setting the air distribution over a cam disc. The air distribution flap motor has no way of recognizing the actual position. To allow the cam disc to be unambiguously positioned despite this, there are two cams of different widths on the cam disc. The microswitch signals to the IHR/IHKR control unit when the cams pass. This mechanism ensures that the cam disc is reliably and promptly positioned.

Convertible program (E93 only)

The convertible program is activated in the factory. (this factory setting can be deactivated in the "Personal Profile".)

Switch-on conditions

1. Terminal 15 ON
2. Convertible top open

The convertible program comprises the following functions

1. The condensation sensor is switched off
2. The blower speed increases with increasing road speed
3. Air distribution is switched to the upper body and head, airflow to the footwell is throttled.
4. Dynamic pressure compensation is changed, i.e. as road speed increases, the volume of air fed into the vehicle through the fresh air grille increases.
5. Solar sensor control variables are changed When the convertible top is open, the solar sensor evaluates the surrounding brightness (darkness to intense sunshine) more strongly. For this reason, the solar sensor has a stronger effect on the IHKA controls when the convertible top is open.

In the convertible program, the blower speed can be changed manually at the IHKA controls. The automatic flap control remains active (no change to flap position).

If the convertible program is active and the flap positions are changed with the CID and controller, the convertible program will be deactivated. This means that manual settings will be assumed, unchanged settings will revert to those that the air-conditioning system had before the convertible top was closed.

The convertible program can be completely reactivated by pressing the AUTO button.

Independent heater (option 536)

The independent heating function is activated either via the Central Information Display (CID) or via Telestart (through the Car Access System (CAS)). There are 2 ways of switching the system on via the CID

Direct operation or programming using the timer.

Automatic rear air conditioning (option 4NB, E70 only)

The automatic rear air conditioning provides for separate temperature and blower settings for the left and right sides in the 2nd row of seats.

Additional heating/ventilation for 3rd row of seats (option 4NC, E70 only)

A rear compartment blower draws air in under the seats in the 3rd row of seats and blows it out through the ventilation air outlet between the seats in the 3rd row of seats.

Seat heating and active seat ventilation in front

If the seat heating/active seat ventilation button is pressed, the IHKA control unit sends the status as a K-CAN message.

Depending on the equipment version of the seat, the message is received either by the seat modules or by the Junction Box electronics (JBE).

1. Message direct to the seat modules: The seat heating and the active seat ventilation are actuated by the respective seat module according to the control logic at the IHKA control panel.
2. Message via Junction Box electronics: The Junction Box electronics transmits a message to the seat modules in the form of a pulse-width modulated signal (PWM signal). The seat heating is actuated by the respective seat module according to the control logic at the IHKA control panel.

If the energy management system requires a reduction in output, the heater and blower output may be reduced in 3 stages or switched off completely

1. Heating and blower output are reduced from level 3 to level 2
2. Heating and blower output are reduced to 50 percent of level 2
3. Seat heating and active seat ventilation are switched off

Seat heating in rear without automatic rear air conditioning

When the seat heating switch for the rear is pressed (2 levels), the seat heating is directly actuated.

If the energy management system requires a reduction in output, the seat heating in the rear may be switched off by a relief relay.

Seat heating in rear with automatic rear air conditioning

The seat heating switches are located in the FKA control panel.

The status of each seat heating switch is transmitted to the respective seat module (rear seat, driver's side and rear seat, passenger side) by means of a pulse-width modulated signal (PWM signal). If the energy management system requires a reduction in output, the heater output may be reduced in 3 stages or switched off completely.

Steering wheel heating (E70 only)

The steering wheel heating is integrated in the Steering Column Switch (SZL). The IHKA control unit transmits the signal for the steering wheel heating to be switched off (power-down command).

Electric steering column adjustment (E70 only)

The electric steering-column adjustment allows the driver to set the steering wheel to the best possible position. This is done with a switch on the left-hand side of the steering column. The tilt and the fore-and-aft setting of the steering column can be electrically adjusted.

Power for the electric steering column adjustment is provided via terminal 30g.

The IHKA control unit actuates the electric steering column adjustment.

When the steering column is adjusted, a Hall sensor on the steering column adjustment motor sends a signal the IHKA control unit. The position of the steering column is registered and stored by the IHKA control unit.

The position of the steering column can be stored for the Key Memory.

The tilt adjustment moves to the highest possible position to make it easier to get in and out of the vehicle.

For the easy-access facility, the steering-column adjustment is automatically activated under the following conditions

1. Terminal R OFF
2. Terminal R ON and driver's door opened (signal via door contact)
3. Terminal 15 OFF with driver's door open (signal via door contact)

The steering-column memory is activated under the following conditions

1. One of the two memory buttons is pressed (from terminal R ON).
2. Another ID transmitter is used (personalization). Condition: The selection "Last seat position after unlocking" is activated in the "Settings" menu in the Central Information Display (CID).

In both cases, the steering-column memory will not move the steering column to the stored position until terminal 15 is switched ON.

National versions

Temperature display in °C (Celsius) or °F (Fahrenheit) can be selected with an on-board computer function.

Subject to change.

Scheme 112

Introduction

The independent heating (made by Webasto) will be installed for the first time on the E90, E91 from 09/2005. The independent heating comprises the independent auxiliary heater and the associated components and power supply. The independent heating is incorporated in the integrated automatic heating/air-conditioning system (IHKA).

1. E70: heating and air-conditioning system controlled on the water side.
2. E90, E91, E92, E93: heating and air-conditioning system controlled on the air side.

The main element of the new independent auxiliary heater is a Venturi burner. This optimizes the entire combustion process to make it considerably more efficient than compared to previous burner technology.

Advantages of the new independent auxiliary heater compared to the auxiliary heater units previously used at BMW

1. Faster start-up and shut-down procedure
2. More rapid stabilization of the combustion process (the maximum heating capacity (5 kW) can therefore be reached faster)
3. Weight of auxiliary heater unit reduced by approx. 20 %
4. The auxiliary heating system requires approx. 30 % less space in the vehicle

Brief description of components

The following components send signals to the auxiliary heating system

1. Telestart transmitter The Telestart transmitter sends the signal to switch the auxiliary heating on and off to the CAS control unit.
2. Temperature sensor in auxiliary heater circuit The temperature sensor in the auxiliary heater registers the temperature in the heating circuit. The signal is processed in the control unit for the auxiliary heater. The control unit therefore controls full-load operation, part-load operation and control pause.
3. Temperature sensor for overtemperature protection The temperature sensor in the auxiliary heater registers the operating temperature. The overtemperature protection facility protects the auxiliary heater from impermissibly high operating temperatures.

The following control units are involved in the auxiliary heating system

1. IHKA control panel and IHKA control unit The IHKA controls and the IHKA control unit are combined in a single component. The IHKA control unit is connected to the K-CAN and LIN bus. The IHKA control unit outputs all the requests for the independent heating function as a message on the K-CAN and the LIN bus. A flashing symbol in the display indicates when the independent heating is in operation. From terminal R it is possible to specify the desired interior temperature for the independent heating function during independent heating operation at the IHKA controls. The set temperature is shown in the display of the IHKA control panel.
2. JBE: Junction box electronics The JBE is an integral part of the junction box. The junction box consists of the JBE and the power distributor. The power distributor provides the power for the auxiliary heater. The JBE is connected via the K-CAN to the bus system. E70 NOTE: The JBE controls the water valve for metering the throughflow of coolant to the heat exchanger. The water valve works electromagnetically and meters the coolant flow rate to the heating system heat exchanger as it is needed. This determines the temperature of the air used for heating the vehicle interior. In the case of automatic air conditioning with separate adjustment for the driver and passenger sides, a duo water valve is installed on account of the left/right separation of the heat exchanger. E90, E91, E92, E93 NOTE: The JBE controls the water valve and the auxiliary water pump. The water valve controls the supply to the independent auxiliary heater either from the radiator supply or from the heat exchanger return flow. In the E70 the switchover valve controls the supply to the independent auxiliary heater. Activation is effected on the prompt of the IHKA control unit via the K-CAN.
3. CAS: Car Access System The Telestart receiver receives the radio signals from the Telestart transmitter and forwards them to the CAS control unit. In turn, the CAS control unit sends a message on the K-CAN. Signal path: Telestart transmitter -> Telestart antenna -> Telestart receiver -> direct wire -> CAS -> K-CAN -> IHKA control unit -> LIN bus -> SHZH control unit
4. DME or DDE: Digital motor electronics or digital diesel electronics E90, E91, E92, E93 The DME or DDE sends the message to switch the water valve on and off. The water valve or switchover valve is switched on and off depending on the coolant temperature.
5. M-ASK or CCC or CHAMP: Multi-audio system controller or Car Communication Computer or multimedia platform The controller signals for selecting the menu are processed in the M-ASK or CCC or CHAMP (multimedia platform: CHAMP; Central Head Unit and Multimedia Platform).
6. CON and CID: Controller and Central Information Display Operation of the auxiliary heater is selected and activated with the controller in the CID. Selection: Direct operation or programming using timer E90, E91, E92, E93 NOTE: Activation of auxiliary heating by BMW "Professional" radio If no CID is installed, operation of the auxiliary heating system can be activated by means of option 663 "BMW Professional radio". Selection: Direct operation or programming using timer
7. KOMBI: Instrument cluster The instrument cluster sends the outside temperature and the time in the form of a message on the K-CAN. The instrument cluster manages the timer function in the event of timer programming.

The following components are controlled

1. SHZH: Independent/auxiliary heater A control unit is installed in the independent auxiliary heater. The SHZH control unit controls and monitors independent auxiliary heating operation. The SHZH control unit is actuated by the IHKA control unit via the LIN bus.
2. Fuel metering pump The metering pump supplies fuel to the auxiliary heater (diesel or gasoline). The SHZH control unit directly controls the metering pump. The metering pump is installed on the vehicle underbody in the vicinity of the fuel tank. NOTE: Independent auxiliary heater with new metering pump in E90, E91 with diesel engine As from 09/2006 vehicles with diesel engines will feature an independent auxiliary heater with a new metering pump. An additional valve has been installed in the independent auxiliary heater. This valve prevents diesel fuel from overrunning unmonitored in the combustion chamber (e.g. due to thermal expansion of the fuel). The metering pump has been adapted accordingly. Thus, when an "old" independent auxiliary heater (up to 09/2006 without additional valve) must be replaced by a "new" independent auxiliary heater (from 09/2006 with additional valve), it is also necessary to replace the metering pump. If only the metering pump is replaced, it is important to pay attention to the part number (metering pump for independent auxiliary heater without additional valve or metering pump for independent auxiliary heater with additional valve).
3. Auxiliary water pump E90, E91, E92, E93 The auxiliary water pump serves the purpose of providing the necessary flow of coolant through the heating circuit at low engine speeds and/or in auxiliary heating mode. The auxiliary water pump is actuated by the junction box electronics (JBE). The IHKA control unit provides the signal to switch the auxiliary water pump on and off. The auxiliary water pump is installed on the frame side member at the level of the left suspension strut tower. Vehicles with 6-cylinder gasoline engine N52 Vehicles with the N52 engine are equipped with an electric coolant pump. These vehicles therefore have an auxiliary water pump only if they are equipped with option 536 "Auxiliary heating". The auxiliary water pump is installed on the auxiliary heater in the heating circuit. E70 If option 536 "Independent heating" is installed, then the auxiliary water pump is omitted. The function is assumed by the circulating pump on the independent heating.
4. Water valve E90, E91, E92, E93 The water valve is installed only in connection with option 536 "Independent heating". The water valve and auxiliary water pump are combined to form one component. The water valve controls the supply to the independent auxiliary heater as follows: From the radiator feed or From the return flow from the heating system heat exchanger (In the E70 the switchover valve controls the supply to the independent auxiliary heater.) The junction box electronics (JBE) actuates the water valve. The switch-on and switch-off message comes from the DME or DDE as well as from the IHKA control unit. The water valve with auxiliary water pump is installed on the frame side member at the level of the left suspension strut tower. Vehicles with 6-cylinder gasoline engine N52 The water valve is installed on the frame side member at the level of the left suspension strut tower. (The auxiliary water pump is installed on the auxiliary heater in the heating circuit.)
5. Switchover valve E70 The switchover valve is installed only in conjunction with option 536 "Independent heating". The switchover valve controls the supply to the independent heating as follows: From the radiator feed or From the return flow from the heating system heat exchanger The SHZH control unit directly activates the switchover valve. The switch-on and switch-off message comes from the DME or DDE as well as from the IHKA control unit.

The auxiliary heating system incorporates the following functions

1. Switch-on
2. Auxiliary heating operation
3. Pseudo auxiliary heating mode with engine running
4. Low-voltage cutout (via DME/DDE)
5. Overtemperature protection
6. Switch-off

Switch-on

The independent heating function is activated either via the Central Information Display (CID) or via Telestart (through the Car Access System (CAS)).

There are 2 ways of activating the system via the CID: Direct operation or programming using the timer.

In connection with Telestart (via CAS) the average range of the Telestart transmitter is approx. 150 meters.

The range of the Telestart transmitter is limited

1. by obstructions
2. by outside irradiation
3. by the orientation of the aerial

When switching on the independent heating, point the Telestart transmitter vertically upwards.

The LED flashing in the Telestart transmitter does not constitute a verification that the independent heating has been activated.

The CAS forwards the signal from the Telestart transmitter via the body CAN to the IHKA control unit.

In term, the IHKA control unit sends the message via the LIN bus to the auxiliary heater control unit.

When the independent heating is switched on, glow plug, combustion-air fan and auxiliary water pump (E90, E91, E92, E93) or circulating pump (E70) are activated.

The metering pump cuts in after approx. 30 seconds. The flame then ignites within 3 seconds and the auxiliary heating runs in full load mode.

The starting time is approx. 120 to 180 seconds (starting time: time between switching on and full load operation).

Automatically controlled heating operation now begins.

At very low outside temperatures, mist may form at the exhaust outlet of the independent heating (similar to that at the exhaust pipe of the engine).

After starting (flame formation), the heater plug functions as the flame monitor.

The start procedure is repeated automatically if no flame is formed or the flame goes out during the start procedure. The fuel feed is stopped if again no flame is formed. The auxiliary heating system is switched off (entry in fault code memory).

Auxiliary heating operation

The auxiliary heating runs in full load mode after starting.

When the temperature in the independent heating circuit reaches the following value, the independent heating goes into part-load operation.

Changeover to part-load range at

1. E70 Gasoline engine: 80 °C Diesel engine: 82 °C
2. E90, E91, E92, E93 Gasoline engine and diesel engine: 77 °C

In part-load operation the temperature can rise to the following value. This is followed by a control pause.

Changeover to control pause at

1. E70 Gasoline engine: 88 °C Diesel engine: 90 °C
2. E90, E91, E92, E93 Gasoline engine and diesel engine: 83 °C

The independent heating switches back to part-load operation if the temperature drops below the following value during the control pause.

Start from control pause at

1. E70 Gasoline engine: 70 °C Diesel engine: 75 °C
2. E90, E91, E92, E93 Gasoline engine and diesel engine: 65 °C

If the temperature rises again to the following temperature value, the independent heating switches again to control pause.

Changeover to control pause at

1. E70 Gasoline engine: 88 °C Diesel engine: 90 °C
2. E90, E91, E92, E93 Gasoline engine and diesel engine: 83 °C

If the temperature in the heating circuit drops again due to increased heating requirement during part-load operation, the independent heating control unit switches to full-load operation at the following temperature.

Return to full-load operation

1. E70 Gasoline engine: 65 °C Diesel engine: 70 °C
2. E90, E91, E92, E93 Gasoline engine and diesel engine: 60 °C

From terminal R independent heating operation also depends on the desired temperature value set at the IHKA controls.

Pseudo auxiliary heating mode with engine running

When the independent heating is running, pseudo auxiliary heating mode is started when the engine is started. When pseudo auxiliary heating mode is activated, the independent heater indicator lamp goes out. (The indicator lamp shows a flashing symbol in the display of the IHKA control panel.) The independent heating runs on. The metering pump can be heard when it is operation (ticking noise).

If the engine temperature is greater than or equal to the temperature of the independent heating circuit, the system will change from pseudo auxiliary heating mode to normal heating mode. Auxiliary heating is deactivated. Only the auxiliary heating circuit is used in pseudo-auxiliary heating mode.

Low-voltage cutout (via DME/DDE)

The battery's charge level is constantly monitored by the intelligent battery sensor throughout the independent heating operation. If the necessary charge level is not maintained, the IHKA control unit will deactivate the independent heating operation.

Overtemperature protection

The overtemperature protection facility responds at a temperature of approx. 145 °C. Auxiliary heating shuts down and locks.

Switch-off

The IHKA control unit switches off auxiliary heating after the set heating time has elapsed (30 minutes).

Auxiliary heating is switched off manually via the Telestart transmitter or with the aid of the controller in the CID. The heating blower is also switched off.

If auxiliary heating is not switched off by the IHKA control unit, the SHZH control unit automatically switches off auxiliary heating mode after an additional time of 10 minutes (entry in fault code memory).

The afterrunning period starts after auxiliary heating has been switched off. The auxiliary water pump (E90, E91, E92, E93) or circulating pump (E70) and the combustion-air fan continue to run in order to cool the independent heating.

The afterrunning time depends on whether auxiliary heating is switched off in full load mode, partial load mode or in the control pause.

When the run-on time has finished, the auxiliary water pump or circulating pump and combustion-air fan are automatically switched off.

Preconditions for activation

Preconditions for switching on auxiliary heating mode

1. Outside temperature below 15 °C (Only in connection with programming with timer or Telestart. Direct operation is possible at any outside temperature but not while driving.)
2. E70 Fuel reserve (9 liters) not reached, i.e. the fuel reserve telltale light does not light up E90, E91, E92, E93 Sufficient fuel in the vehicles tank for a range of at least 50 km
3. On-board supply voltage OK