Climate Control -- Basic Knowledge -- 203 Chassis: Other Mercedes-Benz C-class W204/S204

Ventilation system, function - GF83.10-P-2000P

MODEL 203.0/ 2/ 7

Shown on model 203 up to 31.3.03

Function

The ventilation prevents windows from fogging up, provides fresh air to the occupants and ensures that uniform and pleasant temperatures in the interior are reached quickly.

In normal operation, when the vehicle is stationary or to increase the air quantity, through-ventilation is achieved with the assistance of the blower motor. Fresh air is drawn in via the air inlet in the engine hood and via the fresh air/air recirculation flap (fresh air position).

Identifying Ventilation System. Scheme 42

Depending on setting of control and operating unit, the air is directed through the air ducts to the air vents in the interior.

In air recirculation mode, air is drawn in from the vehicle interior by the blower motor through the fresh air/air recirculation flap (recirculated air position).

When the ignition is switched off, the fresh air/air recirculation flap is automatically moved into a 50 % fresh air and 50 % recirculated air position. This achieves a significant reduction in the flap closing forces.

Air flows into the trunk through ventilation slots below the rear shelf and flows out of the vehicle again through the rear ventilation.

Blower function - GF83.10-P-2102-02P

Operation

The HEAT (N18) or AAC (N22) control and operating module sends a control voltage of 0 - 100 % over the AC bus to the blower regulator (A32n1). This regulates the operating voltage for the blower motor (A32m1) depending on the control voltage applied from 0 to 100 %.This facilitates control of the blower motor speed from 0 - 100 %.

The blower motor regulator (operating voltage) is influenced by the following factors

1. blower motor output setting manual or AUTO (for automatic air conditioning only)
2. Operating functions: air distribution duct EC or AC-OFF (for automatic air conditioning only) REST (for automatic air conditioning only, utilization of residual engine heat and taxi)
3. Mode status (heating, cooling)
4. Coolant temperature
5. Vehicle speed
6. Fresh air/recirculation flap setting
7. Flap positions
8. Circuit 15 (blower motor (A32m1) ON), starter running (blower motor (A32m1) OFF)

The blower motor output can be increased in relation to outside temperature.

in order to ensure that the windows are not fogged up when outside temperatures are low and the passenger compartment temperature level doesn't drop, the blower motor output is increased at outside temperatures of -10 °C to -15 °C by a maximum of 15 %.

Blower function - GF83.10-P-2102-02PC

Operation

The comfort AAC control and operating module C-AAC (N22/7) sends a control voltage of 0 - 100 % over the AC bus to the blower regulator (A32n1). This regulates the operating voltage for the blower motor (A32m1) depending on the control voltage applied from 0 to 100 %.

This facilitates control of the blower motor speed from 0 - 100 %. The blower motor regulator (operating voltage) is influenced by the following factors

1. blower motor output setting (AUTO/manual)
2. Control functions (EC or AC OFF, REST (residual engine heat utilization), air distribution duct)
3. Mode status (heating, cooling)
4. Intensity of sun
5. Coolant temperature
6. Vehicle speed
7. Fresh air/recirculation flap setting
8. Position of activated carbon filter flap
9. Flap positions
10. Circuit 15 (blower motor (A32m1) ON), starter running (blower motor (A32m1) OFF)

The blower motor output can be increased in relation to outside temperature.

In order to ensure that the windows are not fogged up when outside temperatures are low and the passenger compartment temperature level doesn't drop, the blower motor output is increased at outside temperatures of -10 °C to -15 °C by a maximum of 15 %.

Blower regulator function - GF83.10-P-2103-01P

Operation for automatic heater (HEAT) and automatic air conditioning (AAC)

In automatic heating mode (HEAT) and automatic air conditioning (AAC) the blower controller, in manual operation, is actuated in 6 stages via the blower switch integrated in the control and actuating unit for automatic heating and automatic air conditioning systems as well as via the air conditioning Bus.

In addition, the automatic operating mode of the automatic air conditioning (AAC) can be selected via the AUTO button ( )

Scheme 43

Depending on the actually measured interior space temperature and the set specified temperature, the blower controller then controls the operating voltage for the blower (0 - 100%). This results in control of the blower speed between 0 - 100%.

Function for Automatic comfort air conditioning (C-AAC)

By operating the blower button ( ), a control voltage (0 - 100%) is transmitted to the blower controller via the control and actuating unit of the automatic air conditioning system and the air conditioning Bus. Depending on the existing control voltage, the blower controller then controls the operating voltage for the blower between 0 - 100%. This results in control of the blower speed between 0 - 100%

In addition, the automatic operating mode can be selected via the AUTO button

( )

Depending on the actually measured interior space temperature and the set specified temperature, the blower controller then controls the operating voltage for the blower (0 - 100%). This results in control of the blower speed between 0 - 100%.

The blower controller can be diagnosed in all three systems. The following values can be called up

Scheme 44

1. Current
2. Temperature
3. Voltage
4. Fault memory

Automatic heater (HEAT) and automatic air conditioning (AAC)

Automatic comfort air conditioning (C-AAC)

Multifunction sensor, function - GF83.10-P-2135-02P

Function

The C-AAC [K-KLA] multifunction sensor (B31) records the humidity, ambient temperature and pollutant concentration of carbon monoxide (CO) and nitrogen oxide (NOx) in the outside air. It calculates the dew point from the first two values and sends this with the other values to the comfort AAC control and operating module (N22/7) via the AC bus. The C-AAC [K-KLA] multifunction sensor (B31) operates in the following value ranges

1. Relative air humidity of inducted air from 0 to 100 %
2. Temperature of the intake air from -40 °C to +85 °C
3. Dew point temperature from -40 °C to +85 °C
4. CO concentration between 0 and 200 ppm
5. NOx concentration between 0 and 200 ppm

Using the C-AAC [K-KLA] multifunction sensor (B31), economic control of the refrigerant compressor (A9) is made possible depending on the humidity and improved air distribution with respect to keeping the windows free from fogging.

Automatic recirculated air switching by the C-AAC [K-KLA] multifunction sensor (B31)

Requirements

Scheme 45

1. Ambient temperature > 7 °C
2. Activated charcoal filter button ( illuminated)
3. Refrigeration cycle in operation
4. Time elapsed after detecting circuit 15 more than 120 seconds (heating-up time for C-AAC [K-KLA] multifunction sensor (B31))

If the actual pollutant concentration outside the vehicle detected by the C-AAC [K-KLA] multifunction sensor (B31) and actually present is above an acceptable mean interior air quality, then a signal is sent to the comfort AAC control and operating module (N22/7) via the AC bus so that the system switches to 100% recirculated air. As soon as the pollutant concentration present outside the vehicle is below the assumed, mean interior air quality again, the system is operated with fresh air again (exceptions: recirculated air switched manually; automatic recirculated air due to high outside temperature).

Blower controller position/task/function - GF83.10-P-2141P

MODEL 203

Locating Rear Blower Motor And Rear Blower Motor Control Module. Scheme 46

Rear blower motor function - GF83.10-P-2168-01P

Function

The initialization of the rear blower motor (M2/1) is carried out via the rear blower electronic selector wheel (N22/4) on the rear nozzle.

Following on from the rear nozzle open setting, multi-level activation of the rear blower motor (M2/1) occurs.

A potentiometer, which forwards a signal with the requested blower level to the convenience automatic air conditioning push-button control module, is located at the rear blower electronic selector wheel (N22/4) at the rear nozzle.

The convenience automatic air conditioning push-button control module evaluates this signal, and initializes the rear blower motor (M2/1) via the rear blower motor control module (N22/3).

At the same time, this signal is also forwarded to the blower in the convenience air conditioner housing in order to increase the speed.

Blower motor control module, function - GF83.10-P-2169-01P

Function

Via a potentiometer integrated in the electronic rear blower thumb wheel (N22/4) a control voltage is passed on to the rear blower motor control unit via the comfort AAC control and operating module (N22/7)(N22/3).This then regulates the operating voltage (0 to 12 V) 12V) for the rear blower motor, depending on the control voltage applied (M2/1). This facilitates control of the blower speed from 0 to 100 %.

Air ducting, task - GF83.10-P-2182-01P

Center nozzle

The center nozzles are used to provide targeted ducting and distribution of the air in the front, upper passenger compartment.

Fresh air vent

The ventilation nozzle is used to reduce drafts which are caused by the ventilation of the center nozzle and lateral nozzles.

Defroster outlets for windshield and left and right side windows

The defroster outlets for the windshield and left and right side windows are used for ventilation and to keep the windshield and side windows free from misting up.

Right and left lateral nozzle

The lateral nozzle on the left and right ensures a targeted ducting and distribution of the air to the side windows and the side of the passenger compartment.

Footwell air outlets at left and right

The front footwell air outlet is used for ventilating the left and right front footwells.

Footwell air outlet at rear left and right

The rear footwell air outlet is used for ventilating the rear footwell.

Rear compartment nozzles (with code (580) Air conditioning (or Tempmatic for USA) or code (580) Automatic air conditioning or code (581) Automatic air conditioning or code (581) Comfort automatic air conditioning)

In addition to the air outlets in the rear legroom, the rear compartment nozzles provide additional, specific ventilation of the rear compartment.

Stowage compartment ventilation nozzle (with code (580) Air conditioning (or Tempmatic for USA) or code (580) Automatic air conditioning or code (581) Automatic air conditioning or code (581) Comfort automatic air conditioning)

The stowage compartment air vent is used to ventilate the stowage compartment in the center console.

Air inlet

The air inlet serves to route the fresh air required for ventilation purposes from the ventilation slots in the engine hood to the fresh air flap.

Rear vent

The rear vent allows the air passing through the passenger compartment to exit the vehicle again.

Air ducting, function - GF83.10-P-2182-02P

Center nozzle

The direction of air flow can be controlled via the separately adjustable slats at the center nozzle as desired, either upwards, downwards to the left or right or even to the center.

Using the adjustment wheels, the center nozzle can be opened and closed, individually for each side.

To open, turn the adjustment wheels upward.

Additional function installed in vehicles as of 1.6.02 with code 581 comfort automatic air conditioning

Using the cold-air mix adjustment wheel located in the center of the center nozzle, cold air can be mixed in, which then flows out of the ventilation nozzle at the front to provide a temperature difference between footwell and headroom (warm feet, cool head).

Fresh air vent

The fresh air vent can be opened and closed via the adjusting wheel which is located centrally.

No further adjustment options exist.

The draft appearances possibly caused by the center nozzle and side nozzles can be reduced by opening the fresh air vent.

Right and left lateral nozzle

The direction of air flow can be controlled via the separately adjustable slats at the lateral nozzle as desired, either upwards, downwards to the left or right or even to the center.

To open, turn the adjustment wheel upward.

The lateral nozzle is closed when the adjustment wheel is turned downward all the way.

Windshield defroster outlets and left and right side window

The air supply to the windshield and left and right side window defroster outlets can be opened and closed via the defroster button

1. on the HEAT [HAU] control and operating unit (N18) (without code (580) Air conditioning (or Tempmatic for USA) or without code (580) Automatic air conditioning or without code (581) Automatic air conditioning or without code (581) Comfort automatic air conditioning or
2. on the AAC [KLA] control and operating unit (N22) (with code (580) Air conditioning (or Tempmatic for USA) or code (580) Automatic air conditioning or as of 24.4.04 without code (581) Comfort automatic air conditioning) or
3. on the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Automatic air conditioning or code (581) Comfort automatic air conditioning).

A separate adjustment option does not exist. Temperature-controlled air flows out of the defroster outlets. As a result a longer opening time of the defroster outlets is achieved and thus a more pleasant ventilation of the vehicle interior. Under the following prerequisites, cool air can also flow out in automatic mode of the AAC [KLA] control and operating unit (N22) or of the comfort AAC [KLA] control and operating unit (N22/7)

1. automatic air distribution is set
2. in the event of dry weather recognized by: Air humidity sensor (B31/2) (on vehicles with AAC [KLA] control and operating unit (N22)) C-AAC [K-KLA] multifunction sensor (B31) (on vehicles with comfort AAC [KLA] control and operating unit (N22/7)), to prevent the windows from fogging up.

Footwell air outlet at front left and right

The front footwell air outlet can be opened and closed using the air distribution switch on the HEAT [HAU] control and operating unit (N18) or on the AAC [KLA] control and operating unit (N22) or on the comfort AAC [KLA] control and operating unit (N22/7). A separate adjustment option does not exist. Temperature-controlled air flows out of the front footwell air outlet.

Footwell air outlet at rear left and right

The rear legroom air outlet can be opened and closed using the air distribution switch on the HEAT [HAU] control and operating unit (N18) or on the AAC [KLA] control and operating unit (N22) or on the comfort AAC [KLA] control and operating unit (N22/7). A separate adjustment option does not exist. Temperature-controlled air flows out of the rear footwell air outlet.

Rear compartment nozzle (with code (580) Air conditioning (or Tempmatic for USA) or code (580) Automatic air conditioning or code (581) Automatic air conditioning or code (581) Comfort automatic air conditioning)

The direction of air flow can be set by means of two individually adjustable slats as desired, upwards, downwards, to the left and right. The air volume adjustment wheel can be used to open and close the rear compartment nozzle and to regulate the air flow. To open, turn the air quantity adjusting wheel upwards.

Additional function in vehicles as of 1.6.01 with code (581) comfort automatic air conditioning

The air quantity adjusting wheel is replaced by the rear blower electronic selector wheel (N22/4).

Turning the electronic rear blower selector wheel (N22/4) when the rear nozzle is fully opened enables the rear blower motor (M2/1) to be additionally actuated in several stages.

Stowage compartment air vent (with code (580) Air conditioning (or Tempmatic for USA) or code (580) Automatic air conditioning or code (581) Automatic air conditioning or code (581) Comfort automatic air conditioning)

Open stowage compartment ventilation nozzle: push lever downwards.

Close stowage compartment ventilation nozzle: push lever upwards.

The air quantity which is supplied depends on

1. the air distribution duct setting
2. the air quantity setting
3. the opening position of the storage compartment ventilation nozzle

The air required to ventilate the storage compartment is drawn from the rear nozzle air duct.

The air is able to escape into the rear footwell via a ventilation grill.

The air temperature corresponds approximately to the temperature controlled air emitted from the rear nozzles. This cannot be separately adjusted.

As a result of the confined spatial conditions, extremely high temperatures may occur in the stowage compartment

In the case of heat-sensitive goods, therefore, the ventilation nozzle may be closed during heater operation. Do not cover the storage compartment ventilation nozzle with objects.

Air inlet

The air inlet serves to route the fresh air required for ventilation purposes from the ventilation slots in the engine hood to the fresh air flap.

Any penetrating water is collected by the water collector and routed outwards by the water drainage.

Rear vent

The slatted-type flaps mounted in the rear vent open because of the backpressure of the air flowing through the vehicle and allow it to exit. If there is a negative pressure in the vehicle, as when driving with the windows open or with the sliding roof open, the flaps will be closed automatically through the force of gravity. This way they help to avoid any exhaust, dust or moisture from being drawn into the vehicle.

Heater circuit function - GF83.20-P-2003P

MODEL 203.0/ 2/ 7

Function Of Heater Circuit. Scheme 47

Shown on engine 611

The coolant pump (5) pumps cold coolant through the engine (M). There, the coolant absorbs engine heat. Shortly afterwards the heated coolant is routed through the heat exchanger (8), where the heat is dissipated to the passenger compartment air.

The heater heat exchanger (8) is continuously supplied with coolant, the Duovalves used previously for regulating the flow rate are no longer applicable.

Control is carried out as a function of the temperature desired in the vehicle interior via the blend air flaps which are actuated separately for the left and right sides via the left blend air flap actuator motor and right blend air flap actuator motor.

The coolant reaches the coolant pump (5) again via the coolant return (A) in which the coolant circulation pump (M13) is located. By far the larger part of the coolant does not flow through the heater, but from the engine (M) to the coolant thermostat (4). Depending on the water temperature, it routes the coolant through the radiator (3) or directly to the coolant pump (5).

Heating system heat exchanger function - GF83.20-P-2101-01P

Function

The heated coolant flows through the heating system heat exchanger separately for the left and right side.

Coolant flows continuously through the heating system heat exchanger. Depending on the heat output requirement, the control takes place solely through the position of the blend air flaps, by means of the left blending air flap actuator motor (M2/6) and right blending air flap actuator motor (M2/7).

The heat is conducted to the outside via the coiled pipes and fins. This in turn warms the passing air flow, which is directed to the vehicle interior via the various defroster, ventilation and heater vents.

Heater box function - GF83.20-P-2103-02P

Heating mode

Identifying Function Of Heater Box Heating Mode. Scheme 48

Heater operation, function

During heater operation, the intake air (A) is drawn in by the blower motor (A32m1) as a function of the position of the fresh air/air recirculation flap. The intake air (A) cleaned by the dust filter (1) is routed, as a function of the position of the blend air flaps, along the heater heat exchanger (4) through which the coolant flows and heated in the process.

The heated air (C) is routed to the respective air outlets as a function of the positions of the footwell flaps, of the defroster flaps and of the ventilation flaps.

Normal mode

Identifying Function Of Heater Box Normal Mode. Scheme 49

Normal mode, function

In normal mode, the intake air (A) is drawn in by the blower motor (A32m1) as a function of the position of the fresh air/air recirculation flap. The intake air (A) cleaned by the dust filter (1) is routed, as a function of the position of the blend air flaps, along the heater heat exchanger (4) through which the coolant flows.

The fresh air drawn in (A) is routed to the respective air outlets as a function of the position of the footwell flaps, of the defroster flaps and of the ventilation flaps.

Blended air mode with recirculated air

Identifying Hot-Water Recirculation Pump. Scheme 50

Blended air mode with recirculated air, function

During blended air mode with recirculated air, the intake air (A) is drawn in by the blower motor (A32m1) as a function of the position of the fresh air/air recirculation flap. After this, part of the intake air (A) is routed, as a function of the position of the blend air flaps, along the heater heat exchanger (4) through which the coolant flows and heated in the process.

The other part oft the interior air drawn in is diverted past the heater heat exchanger (4) and is then blended with the heated air (C) to form mixed air (D). The mixed air (D) is routed, as a function of the position of the footwell flaps, of the defroster flaps and of the ventilation flaps, to the respective air outlets.

Blended air mode

Identifying Function Of Heater Box Blended Air Mode. Scheme 51

Blended air mode, function

In blended air mode, the intake air (A) is drawn in by the blower motor (A32m1) as a function of the position of the fresh air/air recirculation flap and cleaned by the dust filter (1). After this, part of the intake air (A) is routed, as a function of the position of the blend air flaps, along the heater heat exchanger (4) through which the coolant flows and heated in the process.

The other part oft the fresh air drawn in (A) is diverted past the heater heat exchanger (4) and is then blended with the heated air (C) to form mixed air (D). The mixed air (D) is routed to the respective air outlets as a function of the position of the footwell flaps, of the defroster flaps and of the ventilation flaps.

Heater housing task - GF83.20-P-2103-03P

The heater housing serves to house the following components

Scheme 52

1. Heating system heat exchanger (4)
2. Air ducts (5, 7 to 10)
3. Blower motor (A32m1)
4. Fresh air/air recirculation flaps actuator motor
5. Left blend air flap actuator motor
6. Right blend air flap actuator motor
7. Left and right footwell flaps actuator motor
8. Left and right defroster flaps actuator motor
9. Fresh air flaps actuator motor see scheme 14: Identifying Heater Housing Components And Air Flow

The heater housing ensures that the air volume required for vehicle ventilation is distributed to the respective air ducts and air outlets dependent on the desired temperature in the interior compartment.

If actuated accordingly, the following operating modes are performed

1. Normal mode
2. Heating mode
3. Blended air mode

Identifying Heater Box Design With Blower Motor. Scheme 53

Temperature selector wheel, function - GF83.25-P-2102-01P

Function

The desired in-car temperature is set separately for left and right by turning the temperature selector wheel on the automatic heater (N18) or AAC (N22) control and operating unit.

The automatic heater control and operating unit (N18) or AAC (N22) compares the desired temperature with the actual temperature in the vehicle interior. This temperature is measured by the in-car temperature sensor (N70b1) in the overhead control panel control unit (N70). In vehicles with automatic air conditioning, the interior temperature is also measured by the in-car temperature sensor (N22b1) at the AAC control and operating unit (N22).

By comparing the actual values with the specified values, the automatic heater control and operating unit (N18) or AAC (N22) determines the correct position for the blend air flaps and actuates them separately for the left and right sides. The selected temperature is reached and maintained as quickly as possible, if warming or cooling of the interior is necessary.

Automatic heater actuator motor task - GF83.25-P-2180-01P

Fresh air flap/recirculated air flap actuator motor (M2/5)

The fresh air/air recirculation flaps actuator motor (M2/5) serves to close or open the fresh air supply. It is actuated by the HEAT [HAU] control and operating unit (N18) via the AC bus. In air recirculation mode, the recirculation flap is open and the fresh air flap is closed. In fresh air mode, the fresh air flap is open and the recirculated air flap is closed.

Control of the fresh air/air recirculation flap via the HEAT [HAU] control and operating unit (N18)

Manually pressing the air recirculation switch (N18s2) on the HEAT [HAU] control and operating unit (N18) immediately switches the system to 100 % recirculation for a limited time. This is indicated by the LED in the air recirculation switch (N18s2).

Time limit function

1. approx. 30 min at outside temperatures above approx. 7 °C
2. approx. 5 min at outside temperatures below approx. 7 °C

Left blend air flap actuator motor (M2/6) and right blend air flap actuator motor (M2/7)

The left blend air flap actuator motor (M2/6) and the right blend air flap actuator motor (M2/7) are actuated via the AC bus by the HEAT [HAU] control and operating unit (N18), depending on the position of the hot/ cold temperature selector wheels and the actual interior temperature. The position of the respective blend air flap is changed via the left blend air flap actuator motor (M2/6) and the right blend air flap actuator motor (M2/7). As a result, the requested interior temperature is set. The blend air flaps open or close the air passage to the heater heat exchanger in order to blend fresh air and heated air in the correct proportion, thus achieving the desired interior temperature.

Blend air flaps closed: No air through mixing chamber and therefore no air heating

Blend air flaps open: All air flows through the mixing chamber with maximum heating of air

Footwell flap actuator motors left and right (M2/15)

The left and right footwell flaps actuator motor (M2/15) actuates the footwell flaps to regulate the air flow to the front footwell and to the rear footwell. It is actuated by the HEAT [HAU] control and operating unit (N18) via the AC bus. Depending on actuation, the footwell flaps can move to the following positions

1. Defrosting, footwell flaps 0 % opened
2. Residual engine heat utilization (with code (450) Taxi version or code (670) Residual engine heat utilization system (REST [MRA])), footwell flaps 100 % opened
3. Ignition Off, current position is retained

Defroster vent flap actuator motors left and right (M2/16)

The left and right defroster flaps actuator motor (M2/16) actuates the defroster outlet flaps to control the air flow to the windshield defroster outlet and to the side windows defroster outlets. It is actuated by the HEAT [HAU] control and operating unit (N18) via the AC bus. Depending on actuation, the defroster outlet flaps can move to the following positions

1. Defrosting, defroster flaps 100 % opened
2. Residual engine heat utilization, defroster flaps 66 % opened
3. Ignition off, defroster flaps 100 % opened

Vent flap actuator motor (M2/21)

The fresh air flaps actuator motor (M2/21) actuates the ventilation flaps to control the air flow to the center air outlet and to the ventilation nozzle. Depending on the desired air outlet temperature at the center air outlet, it is actuated by the HEAT [HAU] control and operating unit (N18) via the AC bus.

Depending on actuation, the ventilation nozzles can move to the following positions

1. Defrosting, ventilation nozzles 0 % opened
2. Residual engine heat utilization, ventilation nozzles 20 % opened
3. Ignition Off, current position is retained

Ventilation flap control via the center nozzle

The positions of the ventilation nozzles can be set using the 2 selector wheels at the center air outlet.

In the event of a problem, the defined end positions can be retrieved using STAR DIAGNOSIS and checked (evaluation run). An adjustment run must be carried out after the replacement, i. e. the final positions of flap Open and Closed are defined and retained

Automatic heater actuator motor function - GF83.25-P-2180-02P

The HEAT [HAU] control and operating unit (N18) directly actuates the following components located at the heater housing via the AC bus

1. Fresh air and recirculated air flap actuator motor (M2/5)
2. Left blend air flap actuator motor (M2/6)
3. Right blend air flap actuator motor (M2/7)
4. left and right footwell flaps actuator motor (M2/15)
5. left and right defroster vent flaps actuator motor (M2/16)
6. ventilation flaps actuator motor (M2/21)

After switching the ignition on, the position information of the respective flap stored before switching off is transmitted to the actuator motors (M2/5, M2/6, M2/7, M2/15, M2/16 and M2/21) after approx. 30 s. During regulation, the HEAT [HAU] control and operating unit (N18) cyclically transmits a specified value to actuator motors (M2/5, M2/6, M2/7, M2/15, M2/16 and M2/21) via a separate address.

These then decide accordingly on the direction of rotation and automatically move to the desired position. Feedback on the current position is provided upon each of the cyclic specified value requests by the HEAT [HAU] control and operating unit (N18). The HEAT [HAU] control and operating unit (N18) compares the received actual values with the specified values and recognizes whether an actuator motor (M2/5, M2/6, M2/7, M2/15, M2/16 or M2/21) is at its specified position or is still running (relevant when switching off the ignition for saving the actual position).

Protection function

To protect the actuator motors (M2/5, M2/6, M2/7, M2/15, M2/16 and M2/21) and to prevent step losses, they stop in case of a detected undervoltage or overvoltage.

If the voltage has normalized again, the requested specified position is approached again automatically.

Activated charcoal filter, function - GF83.30-P-2113-02P

The activated charcoal filter consists of a large quantity of so-called splitter adsorbers which are distributed evenly across an air-permeable base mat. They constantly adsorb odors and pollutants and release them again after a while in very low concentrations. Both fresh air and recirculated air is filtered.

When the activated charcoal filter is under operation the blower speed is slightly raised.

The activated charcoal filter can be cut in manually using the activated charcoal filter button or automatically via the C-AAC [K-KLA] multifunction sensor (B31).

Air humidity sensor, function - GF83.30-P-2125-01P

The air humidity sensor (B31/2) measures the air humidity of the drawn in outside air to regulate air dehumidification.

The value of the air humidity sensor (B31/2) is passed on to the AAC [KLA] control and operating unit (N22) via the AC bus and is used to regulate the refrigerant compressor (A9) as well as the interior temperature.

As a result, air dehumidification can be reduced at low humidity, which facilitates a more pleasant climate in the vehicle interior.

The air around the evaporator is no longer cooled down to approx. 3 °C, as previously, in order to then be heated back up to the desired temperature (Reheat mode).

Reheat mode only takes place, if the reheat-associated air dehumidification effect is required to keep the windows condensation free when humidity is high. Three different regulation zones, which are dependent on the relative humidity, are defined as shown in the following tables.

The air humidity sensor (B31/2) operates in the following value ranges

1. Relative humidity of intake air from 0 to 100 %
2. Temperature of inducted air from -40 to +85 °C
3. Dew point temperature from -40 to +85 °C

Automatic air conditioning (AAC) component networking - GF83.40-P-0001-02P

Temperature control

Identifying Automatic Air Conditioning (AAC) Component Networking - Temperature Control. Scheme 54

Refrigerant compressor control

Identifying Automatic Air Conditioning (AAC) Component Networking - Refrigerant Compressor Control. Scheme 55

Actuation of engine and air conditioning electric suction fan with integrated control (M4/7)

Regulation Of Comfort Automatic Air Conditioning - Function Diagram. Scheme 56

Comfort closing and opening

Automatic Air Conditioning (AAC) Component Networking - Comfort Closing And Opening. Scheme 57

Automatic air conditioning (AAC), function - GF83.40-P-0001P

MODEL 203.0 /2 /7 up to 31.5.01 with CODE (580) Air conditioning (or Tempmatic for USA)

MODEL 203.0 /2 /7 as of 1.6.01 with CODE (580) Automatic air conditioning

MODEL 203.0 /2 /7 as of 24.4.04 except CODE (581) Comfort automatic air conditioning

The automatic air conditioning (AAC [KLA]) regulates the desired interior compartment temperature in accordance with the driver or front passenger needs in terms of heating, cooling, and air distribution.

The automatic air conditioning (AAC) is operational immediately after the engine is started and produces the last stored temperature-controlled condition before the vehicle was locked. The system operates depending on air humidity (up to 28.6.06) and air temperature. The ambient air is first cooled down by adding cooled air from the evaporator, even at low outside temperatures, and then passes through the heater heat exchanger where it is heated up to the desired interior temperature. The automatic air conditioning (AAC [KLA]) regulates the interior temperature separately for the driver and the passenger-side.

Ventilation

Ventilation ensures aeration in the vehicle interior. Ventilation is achieved with the support of the blower motor (A32m1) during normal operation, when vehicle is stationary or to increase the air flow. The air is distributed in the vehicle interior via air distribution flaps.

In order to prevent window fogging, the footwell flaps are opened fully for approx. 30 seconds after the ignition has been switched on. When the ignition is switched off, the fresh air/air recirculation flap is automatically moved into a 50 % fresh air and 50 % recirculated air position. This achieves a significant reduction in the flap closing forces

Heating circuit

The coolant is heated by the engine. Afterwards, it passes through the heater heat exchanger, from where the heat is delivered to the air in the interior. Via the heater return, which contains the hot water recirculation pump (M13), the coolant is returned to the coolant pump. The hot water recirculation pump (M13) ensures that the coolant is circulated.

Coolant is always flowing through the heater heat exchanger. Temperature control, depending on the temperature desired in the vehicle interior, is carried out via the blend air flaps, which are activated - separately for the left and right side - via the left (M2/6) and right (M2/7) blend air flap actuator motor.

Refrigerant circuit

The refrigerant compressor (A9) compresses the gaseous refrigerant, which causes it to heat up. The refrigerant is passed on to the condenser and thereby cooled down. After being cleaned in the fluid reservoir, the liquid refrigerant is injected into the evaporator.

The refrigerant evaporates and cools down. The refrigerant compressor (A9) again intakes the refrigerant, which has returned to its gaseous form as a result of heat absorption.

Automatic air conditioning (AAC [KLA]) control

The electronic control of the automatic air conditioning (AAC [KLA]) takes place using various components that are interconnected via the Controller Area Network bus class B (interior) (CAN B). The CAN-B is a bi-directional bus, i.e., each connected control unit receives and transmits information.

Temperature control

The desired temperature is achieved or maintained at a constant level by cooling or heating the air.

For a more accurate temperature control, the temperatures of the evaporator, the outside and inside air are read in.

Residual engine heat utilization (with code (450) Taxi version or code (670) Residual engine heat utilization system (REST [MRA]))

The residual engine heat utilization permits to heat the vehicle also when the ignition is switched OFF. The system uses the residual heat of the engine's coolant to accomplish this.

Comfort automatic air conditioning (C-AAC) networking of components - GF83.40-P-0004-01P

Networking of temperature control, shown on vehicle up to 31.5.02

Identifying Automatic Air Conditioning Box - Normal Mode. Scheme 58

Networking of refrigerant compressor control, shown on vehicle up to 23.4.04

Networking Of Refrigerant Compressor Control - Shown On Vehicle Up To 23.4.04. Scheme 59

Networking of Engine and AC electric suction fan with integrated control (M4/7), shown on vehicle up to 23.4.04

Networking Of Engine And AC Electric Suction Fan With Integrated Control (M4/7) - Shown On Vehicle Up To 23.4.04. Scheme 60

Networking of convenience closing and convenience opening functions, shown on vehicle 203.0/2 up to 23.4.04

Networking Of Convenience Closing And Convenience Opening Functions - Shown On Vehicle 203.0/2 Up To 23.4.04. Scheme 61

Convenience automatic air conditioning (C-AAC), function - GF83.40-P-0004P

MODELS 203.0 /2 /7 up to 31.5.01 with CODE (581) Automatic air conditioning

MODELS 203.0 /2 /7 as of 1.6.01 with CODE (581) Comfort automatic air conditioning

Function

The comfort automatic air conditioning (C-AAC) regulates the desired passenger compartment temperature in accordance with the driver or passenger needs in terms of heating, cooling and air distribution. The air conditioning is fully operational after starting the engine and restores the last stored temperature status before locking the vehicle. System operation is sensitive to moisture and temperature; even at low outside temperatures the ambient air is first cooled down by way of the evaporator's supply of cold air, and then routed through the heat exchanger and set to the desired passenger compartment temperature. The comfort automatic air conditioning (C-AAC) controls the interior temperature and the air distribution separately for the driver and passenger sides.

The comfort automatic air conditioning (C-AAC) can be summarized under the following list of sub-functions.

1. Ventilation Ventilation ensures aeration in the vehicle interior. Ventilation is achieved with the support of the blower motor (A32m1) during normal operation, when vehicle is stationary or to increase the air flow. The air is distributed in the vehicle interior via air distribution flaps. In order to prevent window fogging, the footwell flaps are opened fully for 30 seconds after the ignition has been switched on. When the ignition is switched off, the fresh air/air recirculation flap is automatically moved into a 50 % fresh air and 50 % air recirculation position. This achieves a significant reduction in the flap closing forces.
2. Heater circuit Coolant is heated via the engine. The heated coolant is subsequently guided through the heat exchanger, where the heat is emitted into the air in the interior. Via the heater return, which contains the hot water recirculation pump (M13), the coolant is returned to the coolant pump. The hot water recirculation pump (M13) ensures that the coolant is circulated. The coolant flows through the heating system heat exchanger permanently. Depending on the required in-car temperature, control takes place using the blending air flaps, which are activated separately for the left and right sides by the left blending air flap actuator motor (M2/6) and the right blending air flap actuator motor (M2/7).
3. Refrigerant circuit The refrigerant compressor (A9) compresses the refrigerant vapor which is heated up during the process, routed into the condenser and thus cooled down. After being cleaned in the fluid reservoir, the liquid refrigerant is injected into the evaporator. The refrigerant evaporates and cools down. The refrigerant compressor (A9) again intakes the refrigerant, which has returned to its gaseous form as a result of heat absorption.
4. Comfort automatic air conditioning (C-AAC) control The electronic control of the comfort automatic air conditioning (C-AAC [K-KLA]) takes place using various control units that are interconnected via the class B (interior) Controller Area Network Bus (CAN-B). The CAN-B is a bi-directional bus, i.e. each connected control unit receives and transmits information.
5. Comfort automatic air conditioning (C-AAC) temperature control The desired temperature is achieved or maintained at a constant level by cooling or heating the air. An exact temperature control is achieved by the reading in various temperature sensors.
6. Residual engine heat utilization Residual engine heat utilization enables the vehicle to be heated even when the ignition is OFF. To do so the system utilizes the residual heat from the engine and leads it into the passenger compartment via the blower motor (A32m1). The hot water recirculation pump (M13) ensures that the coolant is circulated.

Refrigeration cycle function - GF83.40-P-2001P

MODEL 203.0 /2 /7 with CODE (580) Air conditioning (or Tempmatic for USA) with CODE (580) Automatic air conditioning with CODE (581) Automatic air conditioning with CODE (581) Comfort automatic air conditioning

Function diagram

Refrigeration Cycle Function Diagram. Scheme 62

The refrigerant compressor (A9) which is driven by the engine compresses the refrigerant vapor, which heats up in the process. The refrigerant is conducted to the condenser (2).

The surface of the condenser (2) is used to withdraw the compression heat from the refrigerant. The refrigerant liquefies during cooling. As it flows through the fluid reservoir (3) the refrigerant is cleaned of chemical and mechanical impurities. The cooled and liquefied refrigerant flows through the expansion valve (4) into the evaporator (5), which is located in the fresh-air flow. The refrigerant is then vaporized. Through this evaporation process heat is extracted from the fresh air flowing past from outside over the tube and fin system so that air cools down.

The air humidity carried along is converted to condensed water, which is routed to the outside. The air is thus dried. The refrigerant compressor (A9) draws in the refrigerant which has turned gaseous again through the collection of heat and compresses it.

When the engine is running and the blower motor is switched on, the interior can be supplied with cooled air through the various air outlets. The degree of cooling intensity is dependent upon the previously set interior temperature and the output of the blower motor.

Regulation of automatic air conditioning, function - GF83.40-P-2004P

MODEL 203.0 /2 /7 up to 31.5.01 with CODE (580) Air conditioning (or Tempmatic for USA)

MODEL 203.0 /2 /7 as of 1.6.01 with CODE (580) Automatic air conditioning

MODEL 203.0 /2 /7 as of 24.4.04 except CODE (581) Comfort automatic air conditioning

Regulation Of Automatic Air Conditioning - Function Diagram. Scheme 63

The electronic control and regulation of interior temperature, air volume and air distribution is performed by the AAC [KLA] control and operating unit (N22) depending on the preselected settings and the following information

1. Interior temperature, detected by the in-car temperature sensor in the AAC [KLA] control and operating unit (N22) and additionally by the in-car temperature sensor in the overhead control panel control unit (N70) (up to 31.5.02 and as from 1.6.05)
2. Position of the tilting/sliding roof (SHD) (for model 203.0/2 with code (414) Power glass tilting/sliding roof) or panoramic tilting/sliding roof (for model 203.7 with code (413) Panoramic sliding roof), read in by overhead control panel control unit (N70)
3. Position of windows, read in by door control units (N69/1, N69/2, N69/3, N69/4)
4. Air humidity, captured by the air humidity sensor (up to 28.6.06), read in by the AAC [KLA] control and operating unit (N22)
5. Ambient temperature, detected by outside temperature display temperature sensor, read in by front SAM control unit with fuse and relay module (N10/1)
6. Battery voltage, coolant temperature and engine speed, read in by EIS [EZS] control unit (N73)
7. Ground speed, read in via instrument cluster (A1)
8. Pressure and temperature of refrigerant, detected by refrigerant pressure and temperature sensor, read in by front SAM control unit with fuse and relay module (N10/1)
9. Evaporator temperature, detected by evaporator temperature sensor, read in by AAC [KLA] control and operating unit (N22)

Regulation of comfort automatic air conditioning, function - GF83.40-P-2006P

MODEL 203.0 /2 /7 up to 31.5.01 with CODE (581) Automatic air conditioning

MODEL 203.0 /2 /7 as of 1.6.01 with CODE (581) Comfort automatic air conditioning

Function

The electronic control and regulation of interior temperature, air volume and air distribution is accomplished by the comfort AAC control and operating unit (N22/7) dependent upon the programmed settings and the following information

1. The interior temperature, measured by the in-car temperature sensor in the comfort AAC control and operating unit (N22/7) and the in-car temperature sensor (up to 31.5.02) in the overhead control panel control unit (N70).
2. The position of the tilting/sliding roof (on models 203.0/2 with code (414) Electric glass titling/sliding roof) or the Panoramic tilting/sliding roof (on model 203.7 with code (413) Panoramic sliding roof), read in by the overhead control panel control unit (N70).
3. The position of the windows, read in by the door control units (N69/1, N69/2, N69/3, N69/4).
4. The air humidity, the ambient temperature, and the concentration of the pollutants, detected by the C-AAC multifunction sensor, read in by the comfort AAC control and operating unit (N22/7).
5. The solar radiation with the aid of the C-AAC sun sensor (4 in total), read in by the comfort AAC control and operating unit (N22/7).
6. The battery voltage, the coolant temperature, and the engine rpm, read in by the EIS control unit (N73).
7. The ground speed, read in by the instrument cluster (A1).
8. The pressure and the temperature of the refrigerant.
9. The temperature on the evaporator, measured by the evaporator temperature sensor.

Automatic air conditioning box, function - GF83.40-P-2105-02P

Heating mode

Identifying Automatic Air Conditioning Box - Heating Mode. Scheme 64

Heater operation, function

In heating mode, intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. The intake air (A) cleaned by the dust filter (1) is routed past the evaporator (3), dried there and cooled off. Subsequently and corresponding to the position of the blend air flaps, the dried and cooled air (B) is routed past the heater heat exchanger (4), through which coolant flows, and is heated up there. Corresponding to the positions of the footwell flaps, the defroster flaps and the fresh air flaps, the heated air (C) is conducted to the respective air outlets.

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet. The defroster flaps are easily opened. When going from heating mode to cooling mode (mode change), the left and right footwell flaps actuator motor (M2/15) starts to close the footwell flaps.

The condensation water is led to the outside via the condensation drain.

Cooling mode

Identifying Design Of Expansion Valve. Scheme 65

Cooling mode function

In cooling mode, intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. The intake air (A) cleaned by the dust filter (1) is routed past the evaporator (3), dried there and cooled off. The dried and cooled air (B) is subsequently diverted past the heater heat exchanger (4), corresponding to the position of the blend air flaps, and flows directly to the particular air outlets depending on the position of the footwell flaps, the defroster flaps and the fresh air flaps.

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet. In cooling mode the footwell flaps are closed by the left and right footwell fresh air actuators (M2/15). The defroster flaps can be open with dry outside air. The other flaps can be operated manually. When going from cooling mode to heating mode (mode change), the left and right footwell flaps actuator motor (M2/15) starts to open the footwell flaps. The condensation water is led to the outside via the condensation drain.

Normal mode

Normal mode function

In normal mode, intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. The intake air (A) cleaned by the dust filter (1) is routed past the evaporator (3), dried there and cooled off. Subsequently and corresponding to the position of the blend air flaps, a portion of the dried and cooled air (B) is routed past the heater heat exchanger (4), through which coolant flows, and is heated up there. The remaining dried and cooled air (B) is diverted past the heater heat exchanger (4) and is blended with the heated air (C) to form mixed air (D).

In the corresponding position of the footwell flaps, the defroster flaps and the fresh air flaps, the mixed air (D) is conducted to the respective air outlets. In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet.

The defroster flaps can be open with dry outside air. The other flaps can be operated manually.

The condensation water is led to the outside via the condensation drain.

Blended air mode with recirculated air

Identifying Automatic Air Conditioning Box - Blended Air Mode With Recirculated Air. Scheme 66

Mixed air mode with recirculated air function

In mixed air mode with recirculated air, intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. This is routed past the evaporator (3) and is dried and cooled there. Subsequently and corresponding to the position of the blend air flaps, a portion of the dried and cooled air (B) is routed past the heater heat exchanger (4) and is heated up there. The remaining dried and cooled air (B) is diverted past the heater heat exchanger (4), through which coolant flows, and is blended with the heated air (C) to form mixed air (D).

In the corresponding position of the footwell flaps, the defroster flaps and the fresh air flaps, the mixed air (D) is conducted to the respective air outlets.

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet.

The defroster flaps can be open with dry outside air. The other flaps can be operated manually.

The condensation water is led to the outside via the condensation drain.

Automatic air conditioning box, purpose - GF83.40-P-2105-03P

The automatic air conditioning box houses the following components

Scheme 67

1. Evaporator (3)
2. Heating system heat exchanger (4)
3. Air ducts (5, 7 to 10)
4. Blower motor (A32m1)
5. Expansion valve
6. Fresh air/air recirculation flaps actuator motor
7. Left blend air flap actuator motor
8. Right blend air flap actuator motor
9. Left and right footwell flaps actuator motor
10. Left and right defroster flaps actuator motor
11. Fresh air flaps actuator motor see scheme 39: Identifying Automatic Air Conditioning Box Air Flow

The automatic air conditioning box distributes the air that is required to ventilate the vehicle to the relevant air ducts and vents depending on the interior temperature that is required.

When actuated accordingly, the following operating modes are implemented

1. Heating mode
2. Cooling mode
3. Normal mode
4. Blending air mode

Identifying Automatic Air Conditioning Housing Design. Scheme 68

REST button, function - GF83.40-P-2109-01P

Function

The residual engine heat utilization system is switched on by pressing the Rest button ( ) on the HEAT control and operating module (N18) on the taxi version (code 450) or residual engine heat utilization system MRA (code 670a), comfort automatic air conditioning (N22/7) only on model 203 or on the comfort AAC control and operating module(N22)

Scheme 69

When the engine is switched off the residual engine heat utilization system heats the vehicle interior depending on the adjusted temperature on the HEAT control and operating module (N18) on taxi version (code 450) or residual engine heat utilization system MRA (code 450), comfort automatic air conditioning (N22/7) only on model 203 or on the comfort AAC control and operating module (N22) and the ambient temperature.

The vehicle can be heated for approx. 30 minutes with the engine switched off. The function is only possible with the ignition switched off or in position 1. The residual engine heat utilization system is switched off automatically in the event of undervoltage.

In the automatic air conditioning system and the convenience automatic air conditioning system the flaps are in automatic mode and the quantity of air is also automatically adjusted. The residual heat function is switched off

1. if the key is moved to position 2 in the ignition switch
2. after approx. 30 minutes
3. if the battery voltage drops below 11 V.

Engine/air conditioning electric fan - GF83.40-P-2118-01P

Actuation of engine and air conditioning electric suction fan with integrated control (M4/7) shown on automatic air conditioning

Identifying Actuation Of Engine And Air Conditioning Electric Suction Fan With Integrated Control (M4/7). Scheme 70

Depending on the refrigerant pressure or the coolant temperature and the outside temperature, the fan speed is increased infinitely variably.

The AAC [KLA] control and operating unit (N22) or the comfort AAC [KLA] control and operating unit transmits the request for engine and air conditioning electric suction fan with integrated control (M4/7) ON to the EIS [EZS] control unit (N73) via CAN-B (CAN). The EIS [EZS] control unit (N73) receives, via CAN-B (CAN), the coolant temperature, detected by the coolant temperature sensor (B11/4), via the CDI control unit (N3/9) or the ME-SFI [ME] control unit (N3/10) and transmits this value to the front SAM control unit with fuse and relay module (N10/1) via the instrument cluster (A1).

The front SAM control unit with fuse and relay module (N10/1) also receives the refrigerant pressure from the refrigerant pressure and temperature sensor (B12/2) and the outside temperature from the outside temperature indicator temperature sensor (B14).

This input information is passed on to the control unit integrated in the electric suction fan engine and AC with integrated control (M4/7) from the front SAM control unit with fuse and relay module (N10/1).

The input data received by the engine and air conditioning electric suction fan with integrated control (M4/7) are compared by the integrated control unit with stored values and, where applicable, the speed of the engine and air conditioning electric suction fan with integrated control (M4/7) is increased up to 100 %.

When the air conditioning system is switched on, the engine and air conditioning electric suction fan with integrated control (M4/7) runs at around just 20 % output (standard ventilating). The basic ventilation can be switched off under the following conditions

1. Outside temperature < or = 15 °C The outside temperature is detected by the outside temperature display temperature sensor (B14) and is forwarded via CAN-B (CAN) to the AAC [KLA] control and operating unit (N22) or to the comfort AAC [KLA] control and operating unit. The pressure-dependent fan speed remains the same.
2. Vehicle speed > 75 km/h The vehicle speed is forwarded from the ESP and BAS control unit via the instrument cluster (A1) and CDI control unit (N3/9) or the ME-SFI [ME] control unit (N3/10) to the control unit integrated in the engine and air conditioning electric suction fan with integrated control (M4/7). The pressure-dependent fan speed remains the same.

Cut-in of electric suction fan engine and AC with integrated control (M4/7)

The electric suction fan engine and AC with integrated control (M4/7) is actuated with the following values

1. Refrigerant pressure < 12 bar = fan OFF
2. Refrigerant pressure > 20 bar = fan ON (100 %)
3. Refrigerant pressure 12 to 20 bar = continuous linear speed increase of suction fan (20 to 100 %)

For the engine and air conditioning electric suction fan with integrated control (M4/7) to continue running even when the refrigerant compressor (A9) is shut down temporarily via the anti-icing protection, a run-on time of approx. 60 seconds is possible.

Condenser function - GF83.40-P-2120-01P

The refrigerant that is compressed and thereby heated by the refrigerant compressor (A9) is introduced into the condenser at the top. The condenser, which heats up, emits heat across its surface to the outside air flowing past it. This in turn cools the refrigerant.

While the refrigerant is cooling down to a specific, pressure-sensitive temperature, the refrigerant condenses and is liquefied. The liquid refrigerant exits at the bottom of the condenser and flows into the fluid reservoir.

Evaporator, function - GF83.40-P-2121-01P

The refrigerant, which is under high pressure, is injected into the evaporator.

The refrigerant evaporates, thereby absorbing the quantity of heat required for evaporation from the air flowing past the evaporator.

The soldered semicircular disks with corrugated ribs provide a large evaporation surface and guarantee rapid heat exchange. The humidity which condenses during the air cooling process is diverted by way of condensed water drainage hoses into the open.

Expansion valve, function - GF83.40-P-2123-01P

When the refrigerant compressor is switched on the pressure in the evaporator drops, thereby causing the diaphragm (1) to curve downwards. The tappet (3) follows the diaphragm movement and presses the valve ball (4) against the spring (5) away from its seat. The opened valve enables the refrigerant to be sprayed into the evaporator.

As the diaphragm movement (1) is dependent on both the intake pressure and the temperature at the evaporator outlet, only the specific quantity of refrigerant, as required for optimum vaporization, is injected.

Identifying Function Of Expansion Valve. Scheme 71

Air conditioning coolant temperature sensor, function - GF83.40-P-2125-01P

The coolant temperature sensor (B11/4) records the temperature of the coolant and passes on the value determined via the EIS [EZS] control unit (N73) and Controller Area Network bus class B (interior) (CAN-B) to the AAC [KLA] control and operating unit (N22) or to the comfort AAC [KLA] control and operating unit (N22/7) (for model 203).

At a coolant temperature of 117 to 127 °C the output of the refrigerant compressor (A9) is reduced linearly.

At temperatures above 127 °C the refrigerant compressor (A9) is shut off by the AAC [KLA] control and operating unit (N22) or comfort AAC [KLA] control and operating unit (N22/7) (in model 203) via CAN-B and front SAM control unit with fuse and relay module (N10/1) (in model 203) or the driver SAM control unit (in model 230). The coolant temperature sensor (B11/4) operates in a value range between -40 and +214 °C.

Comfort automatic air conditioning housing, task - GF83.40-P-2170-02P

The comfort (AAC) automatic air conditioning housing serves to locate the following components

Scheme 72

1. Activated charcoal filter (2)
2. Evaporator (3)
3. Heating system heat exchanger (4)
4. Air deflector flaps (5 to 10)
5. Blower motor (A32m1)
6. Expansion valve
7. Activated charcoal filter flap adjustment motor
8. Fresh air/air recirculation flaps actuator motor
9. Left blend air flap actuator motor
10. Right blend air flap actuator motor
11. Left defroster vent flap actuator motor
12. Right defroster vent flap actuator motor (Scheme 69): Identifying Comfort Automatic Air Conditioning Housing Air Flow
13. Left footwell flap actuator motor
14. Right footwell flap actuator motor
15. Left fresh air flap actuator
16. Right fresh air flap actuator

The comfort automatic air conditioning housing ensures that the required air is distributed for the vehicle ventilation to the respective air ducts and air outlets dependent on the desired temperature in the interior compartment.

When actuated accordingly, the following operating modes are implemented

1. Heating mode
2. Cooling mode
3. Normal mode
4. Blending air mode

Convenience automatic air conditioning box, function - GF83.40-P-2170-03P

Heating mode

Identifying Convenience Automatic Air Conditioning Box - Heating Mode. Scheme 73

Heating mode with activated charcoal filter function

Settings

1. EC/AC OFF Off
2. Both AUTO buttons engaged
3. Activated charcoal filter mode On
4. Air recirculation mode Off

Function

In heating mode, intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. The intake air (A) cleaned by the dust filter (1) is led through the two activated charcoal filters (2) to the evaporator (3), where it is dried and cooled. Subsequently and corresponding to the position of the blend air flaps, the dried and cooled air (B) is routed past the heater heat exchanger (4), through which coolant flows, and is heated up.

Corresponding to the positions of the defroster flaps, the footwell flaps and the fresh air flaps, the heated air (C) is conducted to the respective air outlets.

1. Footwell OPEN
2. Fresh air vent OPEN
3. Defroster outlets slightly closed
4. The other flaps can be operated manually

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet.

The defroster flaps are easily opened. In the transition from heating mode to cooling mode (mode change) they are closed.

The condensation water is led to the outside via the condensation drain.

Cooling mode

Identifying Convenience Automatic Air Conditioning Box - Cooling Mode. Scheme 74

Cooling mode with activated charcoal filter function

Settings

1. EC/AC OFF Off
2. Both AUTO buttons engaged
3. Activated charcoal filter mode On
4. Air recirculation mode Off

Function

In cooling mode, intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. The intake air (A) cleaned by the dust filter (1) is led through the two activated charcoal filters (2) to the evaporator (3), where it is dried and cooled. Subsequently and corresponding to the position of the blend air flaps, the dried and cooled air (B) is routed past the heated heater heat exchanger (4).

Corresponding to the positions of the defroster flaps, the footwell flaps and the fresh air flaps, the dried and cold air (B) is then conducted directly to the respective air outlets.

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet.

In cooling mode, the footwell flaps are closed.

The defroster outlet flaps can be open with dry outside air. The other flaps can be operated manually.

In the transition from heating mode to cooling mode (mode change) the footwell flaps are opened.

The condensation water is led to the outside via the condensation drain.

Normal mode

Identifying Convenience Automatic Air Conditioning Box - Normal Mode. Scheme 75

Normal mode with activated charcoal filter function

Settings

1. EC/AC OFF On
2. Both AUTO buttons engaged
3. Activated charcoal filter mode On
4. Air recirculation mode Off

Function

In normal mode (EC/AC OFF lit up), intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. The intake air (A) cleaned by the dust filter (1) is led through the two activated charcoal filters (2) to the evaporator (3), where it is dried and cooled. Subsequently and corresponding to the position of the blend air flaps, a portion of the dried and cooled air (B) is heated up at the heater heat exchanger (4) through which coolant flows.

The remaining dried and cooled air is diverted past the heater heat exchanger (4) and is blended with the heated air (C) to form mixed air (D).

Corresponding to the position of the defroster flaps, the footwell flaps and the fresh air flaps, the mixed air (D) is conducted directly to the respective air outlets.

1. Footwell OPEN
2. Fresh air vent OPEN
3. Defroster outlets slightly closed
4. The other flaps can be operated manually

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet.

The defroster outlet flaps can be open with dry outside air.

Blended air mode with recirculated air

Identifying Convenience Automatic Air Conditioning Box - Blended Air Mode With Recirculated Air. Scheme 76

Mixed air mode with recirculated air and activated charcoal filter function

Settings

1. EC/AC OFF On
2. Both AUTO buttons engaged
3. Activated charcoal filter mode On
4. Air recirculation mode On

Function

In mixed air mode with recirculated air (EC/AC OFF lit up), intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. This is led through the two activated charcoal filters (2) to the evaporator (3) and is dried and cooled there. Subsequently and corresponding to the position of the blend air flaps, a portion of the dried and cooled air (B) is routed past the heater heat exchanger (4), through which coolant flows, and is heated up.

The remaining dried and cooled air (B) is diverted past the heater heat exchanger (4) and is blended with the heated air (C) to form mixed air (D).

Corresponding to the position of the defroster flaps, the footwell flaps and the fresh air flaps, the mixed air (D) is conducted to the respective air outlets.

1. Footwell OPEN
2. Fresh air vent OPEN
3. Defroster outlets slightly closed
4. The other flaps can be operated manually

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet.

The defroster outlet flaps can be open with dry outside air.

Blended air mode without activated charcoal filter

Identifying Convenience Automatic Air Conditioning Box - Blended Air Mode Without Activated Charcoal Filter. Scheme 77

Mixed air mode without activated charcoal filter function

Settings

1. EC/AC OFF On">
2. Both AUTO buttons engaged
3. Activated charcoal filter mode Off
4. Air recirculation mode Off

Function

In mixed air mode without activated charcoal filter, intake air (A) is drawn in by the blower motor (A32m1), corresponding to the position of the fresh air and air recirculation flap. The intake air (A) cleaned by the dust filter (1) is led past the two activated charcoal filters (2) to the evaporator (3), where it is dried and cooled. Subsequently and corresponding to the position of the blend air flaps, a portion of the dried and cooled air (B) is routed past the heater heat exchanger (4), through which coolant flows, and is heated up.

The remaining dried and cooled air (B) is diverted past the heater heat exchanger (4) and is blended with the heated air (C) to form mixed air (D).

In addition, cooled air (B) is diverted directly downstream of the evaporator (3) for indirect fresh air supply, this flow being controlled by means of the cold air blending adjustment wheel at the center air outlet.

Corresponding to the positions of the defroster flaps, the footwell flaps and the fresh air flaps, the mixed air (D) is conducted to the respective air outlets.

1. Footwell OPEN
2. Fresh air vent OPEN
3. Defroster outlets slightly closed
4. The other flaps can be operated manually

The defroster outlet flaps can be open with dry outside air.

Refrigerant pressure and temperature sensor, function - GF83.40-P-2171-01P

The refrigerant pressure and temperature sensor (B12/2) records the refrigerant pressure and the refrigerant temperature and passes on the value determined via the front SAM control unit with fuse and relay module (N10/1) and the Controller Area Network bus class B (interior) (CAN-B) to the AAC [KLA] control and operating unit (N22) or to the comfort AAC [KLA] control and operating unit (N22/7). This value is compared with a filed pressure/temperature curve.

The refrigerant pressure and temperature sensor (B12/2) operates in a pressure range of from 0 to 35 bar and in a temperature range of from -10 to +90 °C.

Shutting of the refrigerant compressor (A9)

The refrigerant compressor (A9) is switched off on reaching the following values.

1. Refrigerant pressure < 1.8 bar = refrigerant compressor (A9) OFF
2. Refrigerant pressure > 30 bar = refrigerant compressor (A9) OFF

Cut-in of electric suction fan engine and AC with integrated control (M4/7)

The electric suction fan engine and AC with integrated control (M4/7) is actuated with the following values

1. Refrigerant pressure < 12 bar = fan OFF
2. Refrigerant pressure > 20 bar = fan ON (100 %)
3. Refrigerant pressure 12 to 20 bar = continuous linear speed increase of suction fan (20 to 100 %)

If the refrigerant level is too low, the refrigerant compressor (A9) is switched off by the AAC [KLA] control and operating unit (N22) or by the comfort AAC [KLA] control and operating unit (N22/7) via the CAN-B and the front SAM control unit with fuse and relay module (N10/1). The EC/AC OFF mode is activated and can no longer be quit.

The system is only capable of functioning again after the fault has been eliminated and the fault memory in the AAC [KLA] control and operating unit (N22) or comfort AAC [KLA] control and operating unit (N22/7) has been erased.

Automatic air conditioning control and operating unit, task - GF83.40-P-2180-01PP

Shown on AAC [KLA] control and operating unit (N22) as from 1.6.02

Identifying Automatic Air Conditioning Control And Operating Unit - Shown On AAC [KLA] Control And Operating Unit (N22) As From 1.6.02. Scheme 78

To regulate the automatic air conditioning (AAC [KLA]), the following tasks are performed by the AAC [KLA] control and operating unit (N22)

1. Synchronizing the temperatures preselected and actually present and controlling the air outlet temperature at the air outlets.
2. Automatic switchover from fresh air to air recirculation mode
3. electrical control of refrigerant compressor
4. operating the engine/AC electric suction fan with integrated control

In addition, the following functions are also regulated by the AAC [KLA] control and operating unit (N22) and the information required for this is sent for further processing on the Controller Area Network bus class B (interior) (CAN-B).

1. Heated rear window
2. Stationary heater (with code (228) Stationary heater)

The AAC control and operating unit (N22) is used to actuate the following

1. Refrigerant compressor via CAN-B
2. Heating water circulation pump
3. Engine and AC electric suction fan with integrated control
4. Heated rear window
5. Blower regulator and all components connected to the AC bus

The following information is sent from the AAC [KLA] control and operating unit (N22) over CAN-B

1. Dew-point temperature The left front door control unit and right front door control unit read in this value, to provide for a heated outside mirror that can be regulated according to individual requirements.

The following information is read in by the AAC [KLA] control and operating unit (N22)

1. In-car temperature sensor (N22b1)
2. evaporator temperature sensor
3. via CAN-B: Outside temperature display temperature sensor Refrigerant pressure and temperature sensor
4. via EIS [EZS] control unit Battery voltage Coolant temperature sensor Engine speed
5. Via the instrument cluster: Vehicle speed
6. Via A/C bus: air humidity sensor

The window and door positions as well as the position of the tilting/ sliding roof (for code (414) Power glass tilting/sliding roof) are read in by the AAC [KLA] control and operating unit (N22) in order to achieve better control quality when they are open.

The averaged value of the interior temperature with a window open, door open and ground speed = 0 km/h is also recorded for a maximum of 2 min. This ensures that the air conditioning system continues operating immediately with the set interior specified temperature.

The following system settings, which were activated before the engine was switched off, are stored by the AAC control and operating module (N22) in the electronic ignition switch control unit.

1. AC OFF mode activated (yes/no)
2. Central automatic mode activated (yes/no)

When the engine is restarted, the status stored in the EIS control unit is reactivated. The AAC push-button control unit (N22) has a diagnostic capability. As a result, any faults which occur are stored in the DTC memory, which can be read out with the aid of STAR DIAGNOSIS.

When replacing the AAC [KLA] control and operating unit (N22), a variant coding must be performed using STAR DIAGNOSIS.

Blower switch (1)

The blower switch (1) controls the output of the blower motor. The blower switch (1) sets the control voltage for the blower regulator in 6 stages and 4 intermediate settings via the AAC [KLA] control and operating unit (N22). This facilitates control of the blower speed from 0 - 100 %.

Temperature selector wheel, left (2) and right (3)

The left temperature selector wheel (2) and right temperature selector wheel (3) are used to preselect the required interior temperature. The desired interior temperature can be set separately for the left and right sides by turning the wheel. The AAC [KLA] control and operating unit (N22) compares the desired temperature with the current interior temperature, which is measured by the in-car temperature sensor (up to 31.5.02 and as of 1.6.05) in the overhead control panel control unit and additionally by the in-car temperature sensor (N22b1) on the AAC [KLA] control and operating unit (N22).

Using the comparison between specified and actual values, the AAC [KLA] control and operating unit (N22) determines the correct setting of the blend air flaps and actuates these separately. The selected temperature is reached and maintained as quickly as possible, if warming or cooling of the interior is necessary.

Air distribution switch (4)

The air distribution switch (4) controls the air flow to the air outlets for ventilation of the passenger compartment.

The air distribution can be set manually or automatically

1. Manually by turning the air distribution switch (4)
2. Automatically by pressing the Auto button (6)

By turning the air distribution switch (4) on the AAC [KLA] control and operating unit (N22), the fresh air/air recirculation flaps actuator motor, the left blend air flap actuator motor, the right blend air flap actuator motor, the left and right footwell flaps actuator motor, the left and right defroster flaps actuator motor and the fresh air flaps actuator motor are actuated via the AC bus for air distribution.

Apart from the 4 basic settings, a further 8 intermediate settings can be selected.

Defroster button (5)

By pressing the defroster button (5), the defroster function is initiated, which operates according to the following new logic

1. heating power is controlled by the outside temperature.
2. the entire air flow is directed at the windshield and the front side windows, and the defroster outlets are opened
3. the blown-in air is dehumidified depending on the humidity in reheat mode
4. blend air flaps controlled
5. footwell vents closed
6. blower power at 80 %, can be manually controlled

Air recirculation switch (N22s2)

Briefly pressing the air recirculation switch (N22s2) for < 1.5 s actuates the fresh/air recirculation flaps actuator motor, which actuates the fresh air/air recirculation flap; this in turn closes the fresh air duct and opens the recirculated air duct to enable air to be supplied from the vehicle interior. The LED in the air recirculation switch (N22s2) lights up during air recirculation mode.

Recirculation air convenience closing function

If the air recirculation switch (N22s2) is pressed for longer than > 1.5 s, then along with the air recirculation function all open windows and the tilting/sliding roof (SHD (for code (414) Power glass tilting/sliding roof) in automatic mode are closed (windows and tilting/sliding roof (SHD) must be normalized). The function LED in the air recirculation switch (N22s2) lights up during air recirculation mode. Tilting/sliding roof (SHD) and power windows are operated one after the other in order to avoid current peaks.

If the button is pressed once again for > 1.5 s, the windows and the tilting/sliding roof (SHD) are moved back into the previously stored position and the fresh air and air recirculation flap moves into the fresh air position (function LED in air recirculation switch (N22s2) off). The convenience closing function can only be started if the function LED in the air recirculation switch (N22s2) is not on.

Any window which has been opened manually during this recirculation air phase, remains in this position when the recirculation air function is canceled, all other windows move into the stored position.

The positions of the tilting/sliding roof (SHD) and of the side windows that existed before the start of the closing operation are stored by the overhead control panel control unit or the corresponding door control unit. The windows and the tilting/sliding roof (SHD), which were closed using the comfort closing function, remain closed, if the air recirculation button is operated for < 1.5 s. In this case only the fresh air/recirculated air flap is moved into the fresh air position. The stored positions are canceled when the ignition is switched off.

Auto button (6)

Automatic mode can be activated for the left and right sides simultaneously by pressing the Auto button (6).

In automatic mode, in addition to temperature control the blower output and air distribution are controlled automatically.

The blower speed is continuously controlled depending on the temperature difference between the specified and actual values. For electronic control of the system humidity is also used in addition to interior temperature.

AC OFF button (7)

When the AC OFF button (7) on the AAC [KLA] control and operating unit (N22) (LED on) is pressed, the refrigerant compressor is shut off and thus the cooling mode is switched off. The air is no longer cooled and dried.

In vehicles with diesel engines the heater booster control unit is also shut off. All other functions are retained. The pollutant-controlled recirculated air function is not available in AC OFF mode.

In order to shut off the refrigerant compressor, the AAC [KLA] control and operating module (N22) sends the shutoff request and specified value = 0% via the CAN class B to the front SAM control unit with fuse and relay module. At the same time, the refrigerant compressor torque is set to "0" and transferred to the engine electronics and the electronic transmission control (ETC [EGS]) via the EIS [EZS] control unit. The front SAM control unit with fuse and relay module sends the canceled load increase signal to the engine electronics via the EIS control unit and switches the refrigerant compressor off after a defined time delay.

The AC OFF button (7) is installed in the AAC [KLA] control and operating unit (N22) in vehicles up to 31.5.02 as an EC button. The EC button has the same tasks and functions as the AC OFF button (7) which has been installed as from 1.6.02

REST button (for code (450) Taxi version or for code (670) Residual engine heat utilization system (REST [MRA]))

Pressing the REST button, which is combined with the AC OFF button (7), switches off the residual engine heat utilization system. When the engine is switched off, the residual heat heats the vehicle depending on the temperature adjustment on the AAC control and operating module (N22) and the ambient temperature in the vehicle interior. Heating can thus continue for another approx. 30 minutes.

The function is only available when the ignition is switched off or the transmitter key in the EIS [EZS] control unit is in position 1. The residual engine heat utilization system is switched off automatically in the event of undervoltage.

The flaps for the air distribution and the air volume are regulated automatically.

Automatic air conditioning control and operating unit, task - GF83.40-P-2180-01PQ

Shown on AAC [KLA] control and operating unit (N22) up to 31.5.05

Identifying Automatic Air Conditioning Control And Operating Unit - Shown On AAC [KLA] Control And Operating Unit (N22) Up To 31.5.05. Scheme 79

Task

The AAC [KLA] control and operating unit (N22) controls and regulates all climate control functions for the vehicle interior

1. Harmonizing the temperatures preselected and actually present and controlling the air outlet temperature at the air vents.
2. Automatic switchover from fresh air to recirculated air mode
3. Electrical control of refrigerant compressor
4. Operating the engine/AC electric suction fan with integrated control

The following additional functions are also regulated by the AAC [KLA] control and operating unit (N22) and the required information sent to the control units via Controller Area Network bus class B (interior) (CAN B)

1. Heated rear window (HHS)
2. Stationary heater (STH) (for vehicles with code (228) Stationary heater)

The AAC control and operating unit (N22) is used to actuate the following

1. via CAN B: Refrigerant compressor Coolant circulation pump Engine and air conditioning electric suction fan with integrated control Heated rear window
2. via the AC bus: Blower regulator Actuator motors for the air distribution

The following sensor signals are read in by the AAC control and operating unit (N22)

1. Built-in sensor: in-car temperature sensor (N22b1)
2. direct: evaporator temperature sensor
3. Via the AC bus: Air humidity sensor (up to 28.6.06)

The following CAN B signals are read in by the AAC [KLA] control and operating unit (N22)

1. By the front SAM control unit with fuse and relay module: Outside temperature display temperature sensor Refrigerant pressure and temperature sensor
2. By the EIS [EZS] control unit: Battery voltage Coolant temperature Engine speed
3. By the instrument cluster: Ground speed
4. By the overhead control panel control unit: Information of the rain/light sensor (with code (345) Rain sensor) Position of tilting/sliding roof (SHD) (with code (414) Power glass tilting/sliding roof) Position of panoramic roof (with code (413) Panoramic sliding roof)
5. By the restraint systems control unit: Information on the seat occupation status
6. By the door control units: Door status Window position

Blower selector wheel (1)

The blower selector wheel (1) controls the blower output. The blower selector wheel (1) enables the blower output to be set in 6 stages and 6 intermediate positions.

Temperature selector wheel, left (2) and right (3)

The left temperature selector wheel (2) and right temperature selector wheel (3) serve to program the desired temperature in the vehicle interior.

The desired interior temperature is adjusted separately for the left and right by turning the left temperature selector wheel (2) and right temperature selector wheel (3).

Air distribution selector wheel (4)

The air distribution selector wheel (4) can be used to manually set the air distribution for the left and right side of the vehicle interior.

Defroster button (5)

Pressing the defroster button (5) initiates the defrost function. The defroster function is used to prevent the windshield and the front side windows from fogging. To achieve this, the defroster outlets are fully open and the center air outlets and the footwell air outlets are completely closed.

Auto button (6)

Pressing the Auto button (6) enables the blower output and the air distribution to be regulated automatically. Pressing again switches off the automatic function and manual function is restored.

AC button (7)

Pressing the AC button (7) switches off the refrigerant compressor manually or automatically when the desired cooling requirement has been met and thereby shuts off the cooling mode.

Display logic of function LED in the AC button (7)

For vehicles up to 31.5.05, the function LED is off when the refrigerant compressor is on.

For vehicles as of 1.6.05, the function LED is on when the refrigerant compressor is on.

REST button (for code (450) Taxi version or for code (670) Residual engine heat utilization system (REST [MRA]))

Pressing the REST button, which is combined with the AC button (7), switches on the engine residual heat utilization system. With the engine shut off, heating or just ventilation can be continued for another approx. 30 minutes. The function is only possible when the ignition is switched off. The residual engine heat utilization system is switched off automatically in the event of undervoltage.

Heated rear window switch (N22s1)

Pressing the heated rear window switch (N22s1) sends a switch-on request to the rear SAM control unit with fuse and relay module via CAN-B, and the heated rear window is switched on. Simultaneously the function LED in the heated rear window switch (N22s1) is activated.

Air recirculation switch (N22s2)

Briefly pressing the air recirculation switch (N22s2) for < 1.5 s closes the fresh and air recirculation flap to stop air entering from outside. The LED in the air recirculation switch (N22s2) is on during operation. The side windows, the tilting/sliding roof, or the panoramic roof are closed if necessary prior to this by pressing the air recirculation switch (N22s2) for > 1.5 s.

Control and operating unit comfort automatic air conditioning, task - GF83.40-P-2181-01PP

Shown on comfort AAC control and operating unit (N22/7) as of 1.6.02

Identifying Control And Operating Unit Comfort Automatic Air Conditioning - Shown On Comfort AAC Control And Operating Unit (N22/7) As Of 1.6.02. Scheme 80

Task

The comfort AAC control and operating module (N22/7) controls and regulates all air conditioning functions for the vehicle interior.

1. harmonizing the temperatures preselected and actually present and controlling the air outlet temperature at the air vents.
2. Automatic switcher from fresh air to recirculated air mode
3. Electrical control of refrigerant compressor
4. Operating the engine/AC electric suction fan with integrated control

The following additional functions are also regulated by the comfort AAC control and operating unit (N22/7) and the required information forwarded to the processing control units via the Controller Area Network bus class B (interior) (CAN-B).

1. Heated rear window
2. Stationary heater (on vehicles with code (228) stationary heater)

The comfort AAC control and operating module (N22/7) performs the following system actuations

1. via the CAN-B: refrigerant compressor; coolant circulation pump; engine and AC electric suction fan with integrated control; heated rear window
2. via the A/C bus: blower regulator; 10 actuator motors for the air distribution

The following sensor signals are transmitted by the comfort AAC control and operating unit (N22/7) via the CAN-B

1. Sun sensor values: the overhead control panel control unit reads in these values for the automatic driving light actuation in order to achieve a better information flow for this system.
2. Dew point temperature: the left front door control unit and the right front door control unit read in this value in order to implement a demand-based heating of the outside mirrors.

The following sensor signals are received by the convenience AAC push-button control unit (N22/7)

1. installed sensor: in-car temperature sensor (N22/7b1)
2. direct: evaporator temperature sensor
3. via the CAN-B: outside temperature display temperature sensor; refrigerant pressure and temperature sensor
4. via the electronic ignition switch control unit: battery voltage; coolant temperature sensor; engine speed
5. via the instrument cluster: vehicle speed
6. via the A/C bus: C-AAC sun sensor (4 in total); C-AAC multifunction sensor

The comfort AAC control and operating unit (N22/7) reads in the window and door positions as well as the position of the tilting/sliding roof (with code (414) Electric glass titling/sliding roof) in order to achieve an improved control quality in the open position.

The averaged value of the interior temperature with a window open, door open and ground speed = 0 km/h is also recorded for a maximum of 2 min. This ensures that the air conditioning system continues operating immediately with the set interior specified temperature.

The following system settings which were activated before the engine was switched off, are stored by the convenience AAC push-button control unit (N22/7) in the EIS control unit.

1. AC OFF mode activated (yes/no)
2. Activated charcoal filter activated (yes/no)
3. Automatic mode with automatic blower control and left/right air distribution activated (yes/no)
4. At manual setting: Set blower speed and air distribution
5. Set temperatures specified value

When the engine is restarted, the status stored in the EIS control unit is reactivated. The convenience AAC push-button control unit (N22/7) has a diagnostic capability. As a result, any faults which occur are stored in the fault memory which can be read out with the aid of the STAR DIAGNOSIS system.

When the comfort AAC control and operating unit (N22/7) is replaced, a variant coding has to be carried out with the aid of STAR DIAGNOSIS.

Temperature buttons warm (1 and 2) and cold (3 and 4)

Pressing the temperature buttons warm (1 or 2) or cold (3 or 4) on the comfort AAC control and operating unit (N22/7) sets the desired interior temperature separately for left and right.

The comfort AAC control and operating unit (N22/7) compares the desired temperature with the temperature in the vehicle interior, which is measured by the in-car temperature sensor (up to 31.5.02) in the overhead control panel control unit and additionally by the in-car temperature sensor (N22/7b1) on the comfort AAC control and operating unit (N22/7).

By comparing the actual values and the specified values the comfort AAC control and operating module (N22/7) determines the correct position of the blend air flaps and actuates these separately for the left and right. The selected temperature is reached and maintained as quickly as possible, if warming or cooling of the interior is necessary.

Defroster button (5)

Pressing the defroster button (5) initiates the defrost function.

The defroster function works according to the following new logic

1. heating power is controlled by the outside temperature.
2. the entire air flow is directed at the windshield and the front side windows, and the defroster nozzles are opened.
3. the blown-in air is dehumidified depending on the humidity in reheat mode
4. blend air flaps controlled
5. footwell vents closed
6. blower power at 80 %, can be manually controlled

Blower button (6)

The blower button (6) switches the control voltage for the blower regulator in 7 stages (indicated in the display (11) by 7 wedge display segments), depending on the position via the comfort AAC control and operating unit (N22/7). This facilitates control of the blower speed from 0 to 100 %.

AC OFF button (7)

When the AC OFF button (7) on the comfort AAC control and operating unit (N22/7) is pressed (the LED comes on), the refrigerant compressor is shut off and thus the cooling mode is switched off. The air is no longer cooled and dried.

In vehicles with diesel engines the heater booster control unit is also shut off. All other functions are retained. The pollutant-controlled recirculated air function is not available in AC OFF mode.

In order to shut off the refrigerant compressor, the comfort AAC control and operating unit (N22/7) transmits the shutoff request and the specified value = 0 % to the front SAM control unit with fuse and relay unit via CAN-B. At the same time, the refrigerant compressor torque is set to "0" and transferred to the engine electronics and the electronic transmission control via the EIS control unit. The front SAM control unit with fuse and relay module sends the canceled load increase signal to the engine electronics via the EIS control unit and switches the refrigerant compressor off after a defined time delay.

The AC OFF button (7) was installed in the comfort AAC control and operating unit (N22/7) as an EC button in vehicles up to 31.5.02. The EC button has the same tasks and functions as the AC OFF button (7), which was installed as of 1.6.02

Rest button

When the REST button (which is combined with the AC OFF button (7)) is pressed, the residual engine heat utilization is switched on.

When the engine is switched off, the residual heat heats the vehicle depending on the temperature setting on the comfort AAC control and operating module (N22/7) and the ambient temperature in the vehicle interior.

The vehicle can be heated for approx. 30 minutes with the engine switched off. The function is only available when the ignition is switched off or the transmitter key in the EIS control unit is in position 1. The residual engine heat utilization system is switched off automatically in the event of undervoltage.

The flaps for the air distribution and the air volume are regulated automatically.

The residual heat function is switched off

1. if the transmitter key in the EIS control unit is turned to position 2
2. after approx. 30 min. or
3. if the battery voltage drops below 11 V.

Left Auto button (8) and right Auto button (9)

By pressing the left Auto button (8) or right Auto button (9), which are combined with the left and right air distribution switches, the automatic mode for the left and right sides can be activated separately. The system switches back to manual mode by subsequently rotating the air distribution switch.

In automatic mode, in addition to temperature control the blower output and air distribution are controlled automatically.

The blower speed is continuously controlled depending on the temperature difference between the specified and actual values. For electronic control of the system humidity is also used in addition to interior temperature.

In automatic mode, cooled air may also flow out of the defroster vents.

The prerequisites for this are as follows

1. an adjusted automatic air distribution
2. dry weather (recognition of humidity by the C-AAC multifunction sensor) in order to keep the windows free from misting up.

Air distribution switch on left and right

The air distribution can be set manually or automatically

1. Manually (left Auto button (8) or right Auto button (9) not engaged) Turning the air distribution switch on left and right Display by white printed notch
2. Automatically (left Auto button (8) or right Auto button (9) engaged) Display through "AUTO" symbol in display (11)

Turning the air distribution switch on left and right on the comfort AAC control and operating unit (N22/7) actuates the various actuator motors for air distribution via the A/C bus.

Apart from the 4 listed basic settings, a further 8 intermediate settings can be selected.

Activated charcoal filter button (10)

Pressing the activated charcoal filter button (10) on the comfort AAC control and operating unit (N22/7) switches to operation with the activated charcoal filter; this conducts incoming fresh air, after flowing through the dust filter, through the activated charcoal filter. Pressing the activated charcoal filter button (10) actuates the activated charcoal filter flap adjustment motor, which closes the activated charcoal filter flap in the AC housing and thus conducts the air through the activated charcoal filter.

As a result, the pollutant content in the fresh air is reduced and the odor emission decreased. With an increased CO and NOx content in the outside air, recirculated air mode is selected automatically with the aid of the C-AAC multifunction sensor. Air recirculation mode which is regulated as a function of pollutants is not possible in the AC OFF mode and with outside temperatures less than 5 °C.

Display (11)

The display (11) serves to inform the driver about any adjustments to the ventilation and comfort automatic air conditioning. The information is provided in form of the words, symbols and digits.

Dependent on the setting created via the multifunction steering wheel, the temperature is either displayed in °C or in °F in the display (11). Other messages are presented by means of the corresponding symbols.

The display employs a negative technology design, in other words light digits against a dark background.

Air recirculation switch (N22/7s2)

A short press <1,5 s of the air recirculation switch (N22/7s2) actuates the fresh air/air recirculation flap actuator motor, which operates the fresh air/air recirculation flap and thus closes the fresh air opening and opens the recirculation duct in order to enable the air to be supplied from the vehicle interior. The LED in the air recirculation switch (N22/7s2) is illuminated in air recirculation mode.

Recirculation air convenience closing function

If the air recirculation switch (N22/7s2) is pressed for longer than 1.5 s, all open windows and the tilting/sliding roof (with code (414) Power glass tilting/sliding roof) are closed in automatic mode (windows and tilting/sliding roof have to be normalized) in addition to the recirculated air function. The LED in the air recirculation switch (N22/7s2) is illuminated in air recirculation mode. Sliding/tilting roof and power windows are operated one after the other in order to avoid current peaks.

If it is operated once again > 1.5 s, the windows and the tilting/sliding roof are moved back into the previously stored positions and the fresh air/air recirculation flap moves into the fresh air position (function LED off).

The convenience closing function can only be started if the LED in the air recirculation switch (N22/7s2) or the LED in the activated charcoal filter button (10) is not illuminated.

Any window which has been opened manually during this recirculation air phase, remains in this position when the recirculation air function is canceled, all other windows move into the stored position. The positions of the tilting/sliding roof and of the side windows which existed prior to the commencement of the closing operation, are stored by the overhead control panel control unit or by the door control units. The windows and the tilting/sliding roof, which were closed by means of the convenience closing function, remain closed if the air recirculation switch (N22/7s2) is pressed for <1.5 seconds. In this case only the fresh air/air recirculation flap is moved into the fresh air position. The stored positions are canceled when the ignition is switched off.

Control and operating unit comfort automatic air conditioning, task - GF83.40-P-2181-01PQ

Shown on comfort AAC control and operating unit (N22/7) up to 31.5.05

Identifying Control And Operating Unit Comfort Automatic Air Conditioning - Shown On Comfort AAC Control And Operating Unit (N22/7) Up To 31.5.05. Scheme 81

Task

The comfort AAC control and operating module (N22/7) controls and regulates all air conditioning functions for the vehicle interior.

1. harmonizing the temperatures preselected and actually present and controlling the air outlet temperature at the air vents.
2. Automatic switchover from fresh air to recirculated air mode
3. Electrical control of refrigerant compressor
4. Operating the engine/AC electric suction fan with integrated control

The following additional functions are also controlled by the Comfort AAC [KLA] control and operating unit (N22/7) and the required information sent to the processing control units via the Controller Area Network bus Class B (interior) (CAN-B).

1. Heated rear window (HHS)
2. Stationary heater (STH) (for vehicles with code (228) Stationary heater)

The comfort AAC control and operating module (N22/7) performs the following system actuations

1. Via CAN-B: Refrigerant compressor, coolant circulation pump, engine and AC electric suction fan with integrated control
2. Via the A/C bus: Air recirculation unit and 10 actuator motors for air distribution

The following sensor signals are received by the convenience AAC push-button control unit (N22/7)

1. Installed sensor: In-car temperature sensor (N22/7b1)
2. direct: evaporator temperature sensor
3. Via CAN B: Outside temperature display temperature sensor, refrigerant pressure and temperature sensor (via front SAM control unit with fuse and relay module) Battery voltage, coolant temperature sensor, engine speed (via EIS [EZS] control unit) Ground speed (via instrument cluster) Rain/light sensor (for code (345) Rain sensor) (via overhead control panel control unit) Front passenger seat occupied and child seat recognition sensor (via restraint systems control unit)
4. Via the A/C bus: C-AAC [K-KLA] multifunction sensor C-AAC sun sensor (4 in total)

The comfort AAC [KLA] control and operating unit (N22/7) reads in the positions of the windows and doors as well as the position of the tilting/sliding roof (for models 203.0/2 and code (414) Power glass tilting/sliding roof) or Panoramic roof for model 203.7 and code (413) Panoramic sliding roof) to be able to achieve better control quality at an open position.

Left warm temperature button (1) and right warm temperature button (2)

The left warm temperature button (1) and right warm temperature button (2) are used to increase the desired temperature in the vehicle interior. Pressing the left warm temperature button (1) or right warm temperature button (2) on the comfort AAC control and operating unit (N22/7) enables the desired interior temperature to be set for left and right separately.

Left cold temperature button (3) and right cold temperature button (4)

The left cold temperature button (3) and right cold temperature button (4) are used to lower the desired temperature in the vehicle interior. Pressing the left cold temperature button (3) or right cold temperature button (4) on the comfort AAC control and operating unit (N22/7) enables the desired interior temperature to be set for left and right separately.

Defroster button (5)

Pressing the defroster button (5) initiates the defrost function. The defroster function serves to ensure that the windshield and the front side windows are kept free of any fogging. To this end, the defroster vents are opened fully and the center air outlets and footwell outlets fully closed.

Increase blower output button (6)

The increase blower output button (6) is used to increase blower output. The increase blower output button (6) enables blower strength to be increased in 6 stages.

Reduce blower output button (7)

The reduce blower output button (7) is used to lower blower output. The reduce blower output button (7) enables blower strength to be lowered in 6 stages.

A/C button/REST button (8)

Pressing the AC button/REST button (8) on the comfort AAC control and operating unit (N22/7) manually switches off the refrigerant compressor thus deactivating the cooling mode.

When the engine is switched off, the residual engine heat can be used to heat or ventilate for approx. 30 min. The function is only available when the ignition is switched off. The residual engine heat utilization system is switched off automatically in the event of undervoltage.

Display logic of function LED in AC button/REST button (8)

On vehicles up to 31.5.05, the function LED is off when the refrigerant compressor is switched on.

On vehicles as from 1.6.05, the function LED is on when the refrigerant compressor is switched on.

Auto button (9)

Pressing the Auto button (9) automatically controls blower output and air distribution. Pressing the button again switches off the automatic function and the manual function is switched back on.

Activated charcoal filter button (10)

Pressing the activated charcoal filter button (10) on the comfort AAC control and operating unit (N22/7) switches to operation with the activated charcoal filter; this conducts the fresh air, after flowing through the dust filter, through the activated charcoal filter. As a result, the pollutant content in the fresh air is reduced and the odor emission decreased. Where a raised level of CO and NOx in the outside air is detected, air recirculation mode is automatically switched over to. The LED in the activated charcoal filter (10) lights up when the mode is active.

Display (11)

Depending on the setting in the instrument cluster, the temperature in the display (11) is shown either as °C or °F.

Left air distribution thumb wheel (12) and right air distribution thumb wheel (13)

Using the left air distribution thumb wheel (12) and right air distribution thumb wheel (13) enables the air distribution to be manually regulated for the left and right sides in the vehicle interior.

OFF button (14)

Pressing the OFF button (14) completely switches off the comfort AAC control and operating unit (N22/7) and its function requests.

Heated rear window switch (N22/7s1)

Pressing the heated rear window switch (N22/7s1) sends a switch-on request via CAN-B to the rear SAM control unit with fuse and relay module, which switches on the rear window heater. At the same time the LED in the heated rear window switch (N22/7s1) is activated.

Air recirculation switch (N22/7s2)

Pressing the air recirculation switch (N22/7s2) briefly for <1.5 s actuates the fresh air and air recirculation flap.

The fresh air opening closes and the air recirculation opening opens, thus enabling the air in the vehicle interior to circulate and avoiding penetration of any unpleasant odors and pollutants from outside into the vehicle interior; whereby this is contingent on the window and tilting/sliding roof being closed. If the air recirculation switch (N22/7s2) is pressed for longer than 1.5 s, then along with the air recirculation function all open windows and the tilting/sliding roof are automatically closed. If the air recirculation switch (N22/7s2) is pressed again, the windows and the tilting/sliding roof are moved back to their original positions.

Actuator motor, automatic air conditioning, task - GF83.40-P-2182-01P

Fresh air/air recirculation flaps actuator motor (M2/5)

The fresh air/air recirculation flaps actuator motor (M2/5) is used to close or open the fresh air supply by operating the fresh air/air recirculation flap.

By pressing the air recirculation switch (N22s2) at the AAC [KLA] control and operating unit (N22) for < 1.5 seconds, the fresh air/air recirculation flaps actuator motor (M2/5) is actuated via the AC bus.

For recirculated air mode the fresh air supply is closed. Air is drawn by the blower motor (A32m1) from the vehicle interior into the air conditioner housing. For fresh air mode the fresh air supply is open. The blower motor (A32m1) draws in fresh air into the air conditioner housing.

If the air recirculation switch (N22s2) is operated manually the system immediately enters time-limited 100% air recirculation. This is indicated by the LED in the air recirculation switch (N22s2).

Time limit function

1. for approx. 30 minutes at outside temperatures above approx. 7 °C
2. for approx. 5 minutes at outside temperatures below approx. 7 °C
3. for approx. 5 min when the refrigerant compressor (A9) is switched off

After circuit 15 ON, 100 % automatic recirculated air is possible for one time only for approx. 30 min. After expiry of this period the system switches to 80 % recirculated air or fresh air.

Switching off recirculated air function

1. Pressing the air recirculation switch (N22s2) again
2. Activating the defrost function
3. Ignition OFF
4. Expiry of the timeout
5. Switching to AC OFF
6. Switching off the blower motor (A32m1)

Automatic control of the fresh air/air recirculation flaps via the outside temperature

When outside temperatures are high > 20 °C, recirculation is automatically varied from 0 % to 80 % or 100 % in order to cool the vehicle interior more quickly or to reduce the cooling output demand. Once a time limit of approx. 30 min has elapsed, the system automatically switches back from 100 % to maximum 90 % recirculated air.

Blend air flap actuator motor left (M2/6) and blend air flap actuator motor right (M2/7)

The left blend air flap actuator motor (M2/6) and the right blend air flap actuator motor (M2/7) are actuated via the AC bus by the AAC [KLA] control and operating unit (N22) depending on the setting of the hot/ cold temperature selector wheels and the actual interior temperature. The position of the associated blend air flap is altered via the left blend air flap actuator motor (M2/6) and the right blend air flap actuator motor (M2/7). This sets the requested interior temperature. The blend air flaps open or close the passage of air to the heater heat exchanger in order to mix fresh air and heated or cooled air in the correct quantity in order to achieve the desired interior temperature.

Blend air flaps closed: No air through the mixing chamber and therefore no heating of the air.

Blend air flaps open: All air flows through the mixing chamber with maximum heating of air.

Footwell flap actuator motors left and right (M2/15)

The left and right footwell flaps actuator motor (M2/15) actuates the footwell flaps to regulate the air flow to the front footwell and to the rear footwell. It is actuated via the AC bus by the AAC [KLA] control and operating unit (N22) and operates the footwell flaps, which can assume the following positions, depending on the request

1. Defrost, footwell flaps 0 % (closed)
2. Residual engine heat utilization system (with code (450) Taxi version or code (670) Residual engine heat utilization system (REST [MRA]), footwell flaps 100 % open
3. Ignition OFF, previous position is retained

Automatic flap control with engaged Auto button AAC [KLA] control and operating unit (N22)

The footwell flaps are opened linearly up to 100 %, depending on the following values

1. Position of blend air flaps
2. Coolant temperature
3. Evaporator temperature

Left and right defroster flaps actuator motor (M2/16)

The left and right defroster flaps actuator motor (M2/16) actuates the defroster flaps to regulate the air flow to the windshield defroster vent and to the side window defroster vents. It is actuated via the AC bus by the AAC [KLA] control and operating unit (N22) and operates the defroster flaps, which can assume the following positions, depending on the request

1. Defrost, defroster flaps 100 % open
2. Engine residual heat utilization system, defroster flaps 66 % open
3. Ignition Off, defroster flaps 100 % open

Automatic flap control

The defroster flaps are opened linearly up to 100 %, depending on the following values

1. Position of blend air flaps
2. Coolant temperature
3. Evaporator temperature
4. Relative air humidity (up to 28.6.06)

Fresh air flaps actuator motor (M2/21)

The fresh air flaps actuator motor (M2/21) actuates the fresh air flaps for air flow control to the center air outlet and to the fresh air outlet. Depending on the desired air outlet temperature at the center air outlet, it is actuated via the AC bus by the AAC [KLA] control and operating unit (N22) and operates the fresh air flaps, which can assume the following positions, depending on the request

1. Defrost, fresh air flaps 0 % (closed)
2. Engine residual heat utilization system, fresh air flaps 20 % open
3. Ignition OFF, previous position retained

Automatic flap control

Fresh air flaps are up to 25 % open.

The fresh air flaps are opened linearly up to 100 %, depending on the following values

1. Position of blend air flaps
2. Coolant temperature
3. Evaporator temperature

Manual flap control

In manual mode the positions of the fresh air flaps are determined by the 2 selector wheels on the center air outlet.

In the event of a problem, the defined end positions can be retrieved using STAR DIAGNOSIS and checked (evaluation run). An adjustment run must be carried out after being replaced, i.e. the final positions of "flap OPEN" and "flap CLOSED" are defined and retained

Automatic air conditioning actuator motors, function - GF83.40-P-2182-02P

The following components located at the automatic air conditioning box are actuated directly by the AAC [KLA] control and operating unit (N22) via the AC bus

1. Fresh air/air recirculation flaps actuator motor (M2/5)
2. Left blend air flap actuator motor (M2/6)
3. Right blend air flap actuator motor (M2/7)
4. Left and right footwell flaps actuator motor (M2/15)
5. Left and right defroster flaps actuator motor (M2/16)
6. Fresh air flaps actuator motor (M2/21)

An output stage is integrated into the AAC [KLA] control and operating unit (N22), with which the battery voltage for actuating the actuator motors (M2/5, M2/6, M2/7, M2/15, M2/16 and M2/21) can be switched on and off.

After switching on, the actual position of the particular flap that was stored before being shut off is signaled to the corresponding actuator motor (M2/5, M2/6, M2/7, M2/15, M2/16 or M2/21).

During regulation, the AAC [KLA] control and operating unit (N22) cyclically transmits a specified value to the actuator motor (M2/5, M2/6, M2/7, M2/15, M2/16 or M2/21) via a separate address. This then decides accordingly on the direction of rotation and moves automatically to the desired position. The actuator motor signals its instantaneous position in response to every cyclic request for specified value by the AAC [KLA] control and operating unit (N22).

The AAC [KLA] control and operating unit (N22) compares the actual values received with the specified values and thus recognizes whether an actuator motor (M2/5, M2/6, M2/7, M2/15, M2/16 or M2/21) is in its specified position or is still running (relevant when switching off the ignition for storing the actual position).

To protect the actuator motors (M2/5, M2/6, M2/7, M2/15, M2/16 and M2/21) and to prevent step losses, they stop as soon as undervoltage or overvoltage is detected. If the voltage has normalized again, the requested specified position is approached again automatically.

Comfort automatic air conditioning actuator motors, task - GF83.40-P-2183-01P

General information on actuator motors and flap control

Positioning of flaps with resolution < 1 %.

To ensure that the actuator motors do not readjust at each slight change of variable in closed-loop operation, a so-called clearance function has been realized for each flap.

Clearance function

If a position is adjusted once, up to the next change in the position, the influencing relevant to this must not fall below or exceed a defined limit range.

Final values are approached directly (0 %, 100 %).

Flash-fog logic

The flash-fog function prevents the windshield and side windows from becoming fogged up after starting the engine as moist air is not guided directly against the windows after starting, but instead into the footwell of the vehicle.

The Flash-Fog function is aborted if the center level is 100% open during automatic air distribution.

Flap automatic system and manual flap operation

The flaps are immediately moved to a so-called park position via actuator motors following Ignition OFF

1. footwell flaps open
2. defroster flaps closed
3. fresh air and air recirculation flap 50% open
4. all other flaps remain in the last valid position.

Special function for utilization of residual engine heat

The flaps are moved via actuator motors to the following positions 30 ms after residual engine heat utilization ON (with ignition OFF)

1. footwell flaps open
2. defroster flaps 66% open
3. fresh air and air recirculation flap open (fresh air)
4. vent flaps 20% open
5. blend air flaps regulated.

The flaps remain in the park position for the first 30 sec. following ignition ON.

After this time has elapsed, the flap positions for the automatic or manual adjustment apply.

Left fresh air flap actuator motor (M2/19) and right fresh air flap actuator motor (M2/20)

The left fresh air flap actuator motor (M2/19) and the right fresh air flap actuator (M2/20) operate the ventilation flaps for controlling the air flow to the center nozzle and the ventilation nozzle.

Depending on the desired air outlet temperature at the center nozzle the left fresh air flap actuator motor (M2/19) and the right fresh air flap actuator motor (M2/20) are actuated via the comfort AAC control and operating module (N22/7) and the AC bus.

Actuation during "Defrost" Ventilation flaps 0 % open

Actuation during "REST" Ventilation flaps 20 % open

Actuation with ignition off previous setting retained

Automatic flap control

Ventilation flaps 25 % open.

The vent flaps are opened depending on the following values

1. Blending air flap setting
2. Coolant temperature
3. Evaporator temperature

linear up to 100 % open.

Manual flap control

In manual mode the positions of the vent flaps are determined by the 2 selector wheels on the center nozzle.

Blending air flap actuator motor left (M2/6) and blending air flap actuator motor right (M2/7)

The left blending air flap actuator motor (M2/6) and the right blending air flap actuator motor (M2/7) are used to adjust the required in-car temperature.

The left blending air flap actuator motor (M2/6) and the right blending air flap actuator motor (M2/7) are actuated by the comfort AAC control and operating unit (N22/7) and the AC bus depending on the preselection of the temperature buttons and the currently measured interior temperature and move the blending air flaps. The blending air flaps open or close the passage of air through the heating system heat exchanger in order to mix hot air with fresh air or cooled air in order to achieve the desired in-car temperature.

The specified flap angles of the left blend air flap actuator motor (M2/6) and right blend air flap actuator motor (M2/7) are determined by the comfort AAC [KLA] control and operating module (N22/7) depending on the following information

1. set specified temperature value on the temperature push-button
2. in-car temperature measured by the in-car temperature sensor (N22/7b1) in the comfort AAC control and operating unit (N22/7) and up to 31.5.02 by the in-car temperature sensor (N70b1) in the overhead control panel control unit (N70)
3. Coolant temperature

Blend air flaps closed: No air through the mixing chamber and therefore no heating of the air.

Blend air flaps open: All air flows through the mixing chamber with maximum heating of air.

Left defroster vent flap actuator motor (M2/8) and right defroster vent flap actuator motor (M2/9)

The left defroster flap actuator motor (M2/8) and the right defroster flap actuator motor (M2/9) operate the defroster flaps for controlling the air flow to the windshield defroster vent and side window defroster nozzles. By pressing the defroster button on the comfort AAC control and operating module (N22/7) the left defroster flap actuator motor (M2/8) and the right defroster flap actuator motor (M2/9) are actuated via the AC bus and operate the defroster flaps which assume the following positions for different requirements

Actuation during "Defrost" Defroster flaps 100% open

Actuation during "REST" Defroster flaps 66% open

Actuation with ignition off Defroster flaps 100% open

Manual flap control (division as clock by actuating the air distribution wheel)

1 o'clock 2 o'clock 3 o'clock 4 o'clock 5 o'clock 6 o'clock

0 % 0 % 0 % 23 % 74 % 100 %

7 o'clock 8 o'clock 9 o'clock 10 o'clock 11 o'clock 12 o'clock

100 % 100 % 100 % 72 % 15 % 0 %

Automatic flap control

Depending on the following values, the defroster vent flaps are

1. Blending air flap setting
2. Coolant temperature
3. Evaporator temperature.
4. Relative humidity

linear up to 100 % open.

Left footwell flap actuator motor (M2/10) and right footwell flap actuator motor (M2/11)

The left footwell flap actuator motor (M2/10) and the right footwell flap actuator motor (M2/11) operate the footwell flaps that control the air flow to the front and rear footwells.

By rotating the air distribution switch on the comfort AAC control and operating unit (N22/7) the left footwell flap actuator motor (M2/10) and the right footwell flap actuator motor (M2/11) are actuated via the AC bus. The left footwell flap actuator motor (M2/10) and the right footwell flap actuator motor (M2/11) therefore control the footwell flaps which assume the following positions for various requirements

Actuation during "Defrost" Footwell flaps 0 % open

Actuation during "REST" Footwell flaps 100 % open

Actuation with ignition off previous setting retained

Manual flap control (division as clock by actuating the air distribution wheel)

1 o'clock 2 o'clock 3 o'clock 4 o'clock 5 o'clock 6 o'clock

17% 80 % 100 % 100 % 100 % 100 %

7 o'clock 8 o'clock 9 o'clock 10 o'clock 11 o'clock 12 o'clock

65% 14 %0 % 0 % 0 % 0 %

Automatic flap control

The footwell flaps are opened depending on the following values

1. Blending air flap setting
2. Coolant temperature
3. Evaporator temperature

linear up to 100 % open.

Fresh and air recirculation flap actuator motor (M2/5)

The fresh air flap/air recirculation flap actuator motor (M2/5) is used to close or open the fresh air supply by operating the fresh air flaps and air recirculation flaps.

Operating the air recirculation switch (N22/7s2) for <1.5 seconds on the comfort AAC control and operating module (N22/7) actuates the fresh air/air recirculation flaps actuator motor (M2/5) via the AC bus. For air recirculation mode the fresh air supply is closed. Air is drawn by the blower motor (A32m1) from the vehicle interior into the A/C housing.

For fresh air mode the fresh air supply is open. The blower motor (A32m1) draws in fresh air into the A/C housing.

If the air recirculation switch (N22/7s2) is operated manually the system immediately enters time-limited 100% air recirculation. This is indicated by the LED in the air recirculation switch (N22/7s2). Time limit function

1. for 30 minutes at outside temperatures above approx. 7 °C
2. for 5 min at outside temperatures below approx. 7 °C
3. for 5 min with AC OFF.

100 % automatic air recirculation is possible for one time only for 30 min. after the ignition is switched on. After the time has elapsed, the system switches to 80 % air recirculation mode or fresh air mode, depending on the conditions.

Switching off air recirculation function

1. by pressing the air recirculation switch (N22/7s2) again
2. by activating the defroster function
3. through ignition off
4. through expiry of the timeout
5. by changing to AC OFF or
6. by switching off the blower (position 0).

Automatic control of the fresh air and air recirculation flaps via the outside temperatures

At high outside temperatures >20 °C the air recirculation proportion is varied from 0 % to 80 % or 100 % in order to cool down the vehicle interior more quickly or to minimize the cooling output demand. Once a time limit of 30 min. has elapsed, the system automatically switches back from 100 % to maximum 90 % air recirculation.

Automatic control of fresh air and air recirculation flaps via the C-AAC [K-KLA] multifunction sensor (B31)

If the actual pollutant concentration outside the vehicle determined by the C-AAC [K-KLA] multifunction sensor (B31) is above an assumed, mean interior air quality, the system changes to 80% or 100% air recirculation. As soon as the pollutant concentration present outside the vehicle is below the assumed, mean interior air quality again, the system is operated with fresh air again (exceptions: air recirculation switched manually; automatic air recirculation due to high outside temperature).

Activated charcoal filter flap adjustment motor (A32m2)

The activated charcoal filter flap adjustment motor (A32m2) actuates the activated charcoal filter flap to route the air flow through the activated charcoal filter.

By pressing the activated charcoal filter button (LED illuminated) on the comfort AAC control and operating module (N22/7) the activated charcoal filter flap adjustment motor (A32m2) is actuated via the AC bus. Because of this the activated charcoal filter flap in the AC housing is closed, the air drawn in by the blower motor (A32m1) is forcibly cleaned though the two activated charcoal filters.

Note. All of these actuator motors are of identical design.

The assignment to the flap to be actuated and task description of actuator takes place via cable harness coupling.

In the event of a problem, the defined end positions can be retrieved using STAR DIAGNOSIS and checked (evaluation run).

An adjustment run must be carried out after replacing an actuator motor i. e. the final positions of flap OPEN and CLOSED are defined and retained.

Comfort automatic air conditioning actuator motors, function - GF83.40-P-2183-02P

Function

The actuator motors

1. Fresh/air recirculation flaps actuator motor (M2/5)
2. Left blending air flap actuator motor (M2/6)
3. Right blending air flap actuator motor (M2/7)
4. Left defroster vent flap actuator motor (M2/8)
5. Right defroster vent flap actuator motor (M2/9)
6. Left footwell flap actuator motor (M2/10)
7. Right footwell flap actuator motor (M2/11)
8. Left ventilation flap actuator motor (M2/19)
9. Right ventilation flap actuator motor (M2/20)
10. Activated charcoal filter flap adjustment motor (A32m2)

of the comfort AAC housing are actuated directly by the comfort AAC control and operating module (N22/7) via the AC bus.

An output stage is integrated in the comfort AAC (C-AAC [K-KLA]) control and operating unit (N22/7), with which the battery voltage for the actuator motors (M2/5, M2/6, M2/7, M2/8, M2/9, M2/10, M2/11, M2/19, M2/20) and the activated charcoal filter flap adjustment motor (A32m2) can be switched on and off.

After switching on, the actuator motors (M2/5, M2/6, M2/7, M2/8, M2/9, M2/10, M2/11, M2/19, M2/20) and the activated charcoal filter flap adjustment motor (A32m2) are notified of the respective actual flap positions that were stored before switching off.

During control the comfort AAC control and operating unit (N22/7) cyclically transmits a specified value to the actuator motors (M2/5, M2/6, M2/7, M2/8, M2/9, M2/10, M2/11, M2/19, M2/20) and the activated charcoal filter flap adjustment motor (A32m2) via an internal address. This then decides accordingly on the direction of rotation and moves automatically to the desired position. The comfort AAC control and operating unit (N22/7) signals its current position in response to every cyclic request for the specified value. The comfort AAC control and operating module (N22/7) compares the actual values received with the specified values and thus recognizes whether an actuator motor is in its specified position or is still running (relevant when switching off the ignition for storing the actual position).

To protect the actuator motors (M2/5, M2/6, M2/7, M2/8, M2/9, M2/10, M2/11, M2/19, M2/20) and the activated charcoal filter flap adjustment motor (A32m2) and to prevent step losses, they stop as soon as undervoltage or overvoltage is detected. If the voltage has normalized again, the requested specified position is approached again automatically.

Belt pulley, function - GF83.55-P-2103-02P

Function under normal operating conditions

Under normal operating conditions the rubber (2) is deformation resistant. Thus it transmits the belt pulley's (3) torque to the hub (1) and at the same time to the refrigerant compressor shaft, whereby the hub (1) and belt pulley (3) turn in the direction of the arrow.

The refrigerant compressor torque < the rubber torque limit (2). In this operating condition, the rubber (2) acts as a shock absorber by inhibiting resonance via the belt with other engine components.

Identifying Belt Pulley, Function - Function Under Normal Operating Conditions. Scheme 82

Function of refrigerant compressor lock up

When the refrigerant compressor locks up, the torque required to drive the refrigerant compressor must be greater than the torque present on the belt pulley (3). This causes slip to occur between the belt pulley (3) and hub (1) because of the deformation and wear of the rubber (2). Thus the belt pulley (3) continues to rotate even with a locked up refrigerant compressor.

The refrigerant compressor torque > the rubber torque limit (2).

In this operating condition, the rubber (2) acts as a belt pulley protection device.

Identifying Stationary Heater/Heater Booster Control Unit - Model 203 Up To 23.4.04, Models 210, 215, 220, 230 With Code (228) Stationary Heater. Scheme 83

Belt pulley, design - GF83.55-P-2103-03P

The belt pulley (3) is attached to the hub (1) via the rubbers (2), the hub (1) being firmly connected to the refrigerant compressor shaft.

Identifying Belt Pulley, Design. Scheme 84

Pressure relief valve, function - GF83.55-P-2104-02P

The pressure relief valve is a pressure sensitive wax valve. It is used when all other pressure-dependent safety devices cannot prevent a pressure rise in the refrigerant compressor (A9).

The wax can withstand a pressure of approx. 35 bar. If the pressure increases to above this value, the wax fuse is destroyed and pressure is released through the created opening.

Temperature control function - GF83.57-P-2000P

Model 203.0 /2 /7 up to 31.5.01 with CODE (581) Automatic air conditioning

Model 203.0 /2 /7 as of 1.6.01 with CODE (581) Comfort automatic air conditioning

Networking of temperature control, shown on vehicle up to 31.5.02

Function

The electronically controlled cooling, heating and ventilation system of the comfort automatic air conditioning (C-AAC) achieves the desired interior temperature as rapidly as possible or maintains it constantly throughout

1. Cooling of the air by means of the evaporator.
2. the heating system heat exchanger heating the air.

1. Heating mode The in-car temperature sensors (N22/7b1, N70b1) measure the respective interior temperatures. In addition the outside temperature is also determined by the outside temperature indicator temperature sensor (B14), the humidity is determined by the C-AAC multifunction sensor (B31) and the intensity and direction of the solar radiation is determined by the C-AAC sun sensor (4 sensors in total) (B32/2). The electronic control of the comfort AAC push-button control unit (N22/7) compares the various measured values with the temperature preselected at the temperature push-button. Depending on requirements, the electronic circuit regulates the comfort automatic air conditioning (C-AAC), by altering the position of the blend air flaps using the left blending air flap actuator motor (M2/6) and right blending air flap actuator motor (M2/7) or it holds each setting at a constant value.
2. Cooling mode The evaporator temperature sensor (B10/6) measures the air temperature at the evaporator's air outlet while the in-car temperature sensors (N22/7b1, N70b1) detect the respective interior temperature. In addition the outside temperature is also determined by the outside temperature indicator temperature sensor (B14), the humidity is determined by the C-AAC multifunction sensor (B31) and the intensity and direction of the solar radiation is determined by the C-AAC sun sensor (4 sensors in total) (B32/2).

The electronic control of the comfort AAC push-button control unit (N22/7) compares the various measured values with the temperature preselected at the temperature push-button. Depending on requirements, the electronic circuit alters the settings of the comfort automatic air conditioning (C-AAC) by actuating the refrigerant compressor or maintaining the particular setting constant.

The in-car temperature sensor (N70b1) is installed in vehicles up to 31.5.02 and as from 1.6.05 in the overhead control panel control unit. On vehicles between 1.6.02 up to 31.5.05, the interior temperature is determined solely by the in-car temperature sensor (N22/7b1), which is integrated into the comfort AAC control and operating unit (N22/7)

Temperature control function - GF83.57-P-2000PC

MODEL 203.0 /2 /7 up to 31.5.01 with CODE (580) Air conditioning (or Tempmatic for USA)

MODEL 203.0 /2 /7 as of 1.6.01 with CODE (580) Automatic air conditioning

MODEL 203.0 /2 /7 as of 24.4.04 except CODE (581) Comfort automatic air conditioning

Networking Of Temperature Control - Model 203.0 /2 /7 Up To 31.5.01 And As Of 1.6.01 With Code (580) And As Of 24.4.04 Except Code (581). Scheme 85

Temperature control

The electronically controlled cooling, heating and ventilation system of the automatic air conditioning (AAC [KLA]) achieves the desired interior temperature as quickly as possible or holds it at a constant value by

1. the evaporator cooling the air
2. the heating system heat exchanger heating the air

On vehicles from 1.6.02 to 31.5.05, the interior temperature is detected solely by the in-car temperature sensor (N22b1) in the AAC [KLA] control and operating unit (N22)

Heating mode

The in-car temperature sensor (N22b1) or the in-car temperature sensor (N70b1) measure the interior temperature. The outside temperature is recorded by the outside temperature indicator temperature sensor (B14).

The electronic control of the AAC control and operating module (N22) compares the various measured values with the temperature preselected at the temperature selector wheels.

As required, the position of the blend air flaps is either altered or kept constant via the left blend air flap actuator motor (M2/6) and the right blend air flap actuator motor (M2/7).

Cooling mode

The evaporator temperature sensor (B10/6) detects the air temperature at the evaporator's air outlet, the in-car temperature sensor (N22b1) or the in-car temperature sensor (N70b1) detects the interior temperature. The outside temperature is measured by the outside temperature display temperature sensor (B14) and the air humidity by the air humidity sensor (B31/2) (up to 28.6.06).

The electronic control of the AAC control and operating module (N22) compares the various measured values with the temperature preselected at the temperature selector wheels.

As required, the position of the blend air flaps is either altered or kept constant via the left blend air flap actuator motor (M2/6) and the right blend air flap actuator motor (M2/7).

Evaporator temperature sensor, function - GF83.57-P-2102-02P

The evaporator temperature sensor (B10/6) is located in the air flow behind the evaporator. It passes on its resistance value, depending on the temperature at the evaporator, to the AAC [KLA] control and operating unit (N22) (with code (580) Air conditioning (or Tempmatic for USA) or code (580) Automatic air conditioning) or to the comfort AAC [KLA] control and operating unit (N22/7) (with code (581) Automatic air conditioning or code (581) Comfort automatic air conditioning).

The refrigerant compressor (A9) is switched off when the evaporator temperature reaches approx. 2 °C. This serves to prevent the evaporator from icing up.

Outside air temperature sensor function - GF83.57-P-2103-01P

Function

The current value of the outside temperature indicator temperature sensor (B14) is read by the front SAM control unit with fuse and relay module (N10/1).

The outside temperature is calculated using the value from the outside temperature display temperature sensor (B14) and the vehicle speed. The fact that the outside air temperature is dependent on the vehicle speed prevents any excess temperature from being displayed when the car is at a standstill or traveling slowly, e.g. as induced by engine heat radiation.

When switching the ignition on or off and at speeds of less than 20 km/h the last measured resistance value is used.

The outside air temperature is needed for

1. the outside temperature indicator (A1p4)
2. the mirror heaters (M21/1r1 and M21/2r1)
3. the washer nozzle hose heater (R2/11)
4. the washer nozzle heater (R2/1)
5. the interior temperature control and
6. the engine control.

Sun sensor, function - GF83.57-P-2104-01P

Function

The C-AAC sun sensor (4 in total) (B32/2) records the intensity and angle of incidence of the solar radiation on the vehicle.

This enables the in-car temperature and blower speed to be automatically adapted depending upon the level of radiation intensity (brightness).

Moreover, where radiation is of a one-side nature, then a suitable temperature difference is automatically set between the right and left regulated specified temperatures.

The measured value is forwarded to the C-AAC [K-KLA] control and operating module (N22/7) via the AC bus.

Stationary heater/heater booster control unit position - GF83.70-P-4002-01B

The STH control unit (A6n1) for model 129 or the STH or ZUH control unit (A6n1) for models 168, 202, 210 is mounted on the STH heater unit for model 129 or the STH or ZUH heater unit for models 168, 202, 210. Together with the heat exchanger (1), it forms an inseparable unit.

Identifying Stationary Heater/Heater Booster Control Unit Position. Scheme 86

Stationary heater/heater booster control unit, task - GF83.70-P-4002-02A

The task of the STH control unit (A6n1) for models 129, 203, 209, 215, 230 or the STH or ZUH control unit (A6n1) for models 168, 202, 210, 220 or the STH and ZUH control unit (A6n1) for model 463 is to control and monitor overall heater operation

Scheme 87

1. Monitoring the signals from the glow pin unit flame monitor in its function as flame monitor and internal coolant temperature sensing
2. monitoring cut-in with a starter lockout depending on internal coolant temperature sensing in the case of the heater booster
3. Actuation of the combustion air blower, the circulation pump, the external fuel metering pump and the heater fan
4. malfunction shutoff in the event of extraordinary operating conditions such as flame discontinuation, undervoltage or overvoltage, failure of internal coolant temperature acquisition
5. malfunction shutoff and locking in the event of overheating. see scheme 90: Identifying Stationary Heater/Heater Booster Control Unit

The internal coolant temperature recording is integrated into the STH control unit (A6n1) or the STH or ZUH control unit (A6n1). In the event of a malfunction or a defect, the control unit/heat exchanger unit must be replaced

Stationary heater/heater booster control unit, task - GF83.70-P-4002-02P

General

The STH control unit (A6n1) controls heater operation of the heater (A6), or the blower function and thus ensures that the driver's desired interior heating or cooling is performed.

The STH control unit (A6n1) is incorporated into the Controller Area Network bus Class B (interior) (CAN-B).

The following sequences are controlled

1. Interior heating
2. Interior ventilation

Reading-in of senders and sensors

1. Temperature sensor (A6b1)
2. Glow pin unit flame monitor (A6r4)

Control and voltage supply

1. Glow pin unit flame monitor (A6r4)
2. Circulation pump (A6m1)
3. Combustion air blower (A6m2)
4. STH fuel metering pump (Y23)

Discrete inputs

1. Tml. 30
2. Tml. 31
3. STH radio remote control receiver (A6/1)

Residual engine heat utilization function - GF83.75-P-2000P

MODEL 203.0 /2 /7 up to 31.5.01 with CODE (581) Automatic air conditioning

MODEL 203.0 /2 /7 as of 1.6.01 with CODE (581) Comfort automatic air conditioning

MODEL 203.0 /2 /7 with CODE (450) Taxi version with CODE (670) Residual engine heat utilization (REST [MRA])

Function

Residual engine heat utilization enables the vehicle to be heated even when the ignition is OFF.

To do so, the residual engine heat utilization system uses the residual heat from the engine and routes it into the passenger compartment via the blower motor (A32m1). The residual engine heat utilization is only possible when the ignition is switched off.

After pressing the REST button on the HEAT [HAU] control and operating unit (N18) or the AAC [KLA] control and operating unit (N22) (with code (450) Taxi version or with code (670) Residual engine heat utilization system (REST [MRA]) or at the comfort AAC (C-AAC [KKLA]) control and operating unit (N22/7) the following program sequence is specified

1. Blend air flaps controlled
2. Coolant circulation pump (M13) ON
3. Blower motor (A32m1) automatically supplied with a control voltage of 30 %
4. Defroster and footwell flaps are automatically adjusted for approx. 30 seconds
5. Activated charcoal filter flap open (no activated charcoal filter operation possible in vehicles with comfort AAC (C-AAC [K-KLA]) control and operating unit (N22/7))
6. Footwell flaps 100 % OPEN
7. Defroster vent flaps 66 % OPEN
8. Fresh air vents 20 % open
9. Fresh air and air recirculation flap in fresh air position

End of program

1. Repeated actuation of REST button
2. Expiration of the time function of approx. 30 min. (repeated actuation possible)
3. When battery voltage is less than 11 V, the LED on the REST button flashes on and off
4. Ignition On

During residual engine heat utilization only the REST button and the set point adjusters can be actuated, all other function keys are locked