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Fig. 35: Identifying Heater Core
HEATING WATER CIRCULATION PUMP FUNCTION - GF83.20-P-2102-01GI
Function
The quantity of coolant delivered to the heat exchanger when the engine is running is dependent on the coolant
pump. The heating water circulation pump ensures that a constant and bubble-free flow of water is present at
the heat exchanger during residual engine heat utilization, even at low engine speeds.
Initialization of the heating water circulation pump is carried out via the AAC push-button control module
(N22).
Switch-on conditions
Ignition ON
Stationary heater/ON
Enable conditions at residual engine heat complied with
Special conditions
At ambient temperatures of less than -20°C several starting attempts are made, in order to ensure that the
heating water circulation pump goes into operation.
To this end the heating water circulation pump is switched off in intervals of 1 minute for 5 seconds, until the
coolant or blow-out temperature is +20°C higher than the ambient temperature.
Switch-off conditions
Ignition OFF and overshoot time expired
Stationary heater OFF
Residual engine heat OFF and overshoot time expired
Enable conditions at residual engine heat no longer complied with
Enable conditions at residual engine heat
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
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Page 3290 of 4133
The heating water circulation pump runs in any event 1 minute after starting residual engine heat operation. The
overshoot conditions at least will be fulfilled.
Overshoot conditions
Coolant temperature 100°C --> overshoot time 5 minutes
Coolant temperature >100°C --> overshoot time 10 minutes
HEATER HOUSING POSITION - GF83.20-P-2103-01GH
The heater housing (1) is located beneath the instrument panel.
Fig. 36: Identifying Heater Housing
HEATER BOX FUNCTION - GF83.20-P-2103-02GH
Operating condition: Heating
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
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Page 3291 of 4133
Fig. 37: Identifying Heater Box Function - Operating Condition Heating
Operating condition: Heating Function
In the heating operating status, the fresh air (A) is drawn in by the blower (5) into the heater housing and routed
through the dust filter (3). The fresh air (B), which is cleaned by the dust filter (3), is subsequently conducted
through the heat exchanger (1). This air conduction is controlled via the setting of the blending air flaps (6).
The cleaned fresh air (B) is heated up by the heat exchanger (1). The warm air (C) is conducted via the air
outlets (E, F, M and S) into the vehicle interior.
The recirculated air flap (4) is closed.
Operating condition: No heating
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 47 © 2006 Mitchell Repair Information Company, LLC.
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Fig. 38: Identifying Heater Box Function - Operating Condition No Heating
Operating condition: No heating Function
In the "no heating" operating status, the fresh air (A) is drawn in by the blower (5) into the heater housing and
routed through the dust filter (3).
The fresh air (B), which is cleaned by the dust filter (3), is subsequently routed around the heat exchanger (1).
This air conduction is controlled via the setting of the blending air flaps (6).
The cleaned fresh air (B) is routed directly into the passenger compartment via the air outlets (E, F, M and S).
The recirculated air flap (4) is closed.
Operating condition: No "recirculated air" heating
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 48 © 2006 Mitchell Repair Information Company, LLC.
Page 3293 of 4133

Fig. 39: Identifying Heater Box Function - Operating Condition No Recirculated Air Heating
Operating condition: No "recirculating air" heating Function
In the no "recirculated air" heating mode the blower (5) draws the recirculated air (A) from the passenger
compartment over the opened recirculated air flaps (4) into the heater housing and routs it through the dust
cleaner (3). The recirculated air (B), which is cleaned by the dust filter (3), is subsequently routed around the
heat exchanger (1). This air conduction is controlled via the setting of the blending air flaps (6).
The cleaned recirculated air (B) is routed directly into the passenger compartment via the air outlets (E, F, M
and S).
The supply of fresh air is cut off by the recirculated air flap (4).
HEATER HOUSING TASK - GF83.20-P-2103-03GC
The heater housing serves to house the following components
Air ducting flaps
Dust filter
Blower
Series resistor group
Heating system heat exchanger
PTC heater booster (in model 168 with engines OM 668.940/941 as of 01.03.01)
Fresh air/recirculated air flap actuator (with model 168 as of 01.03.01)
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 49 © 2006 Mitchell Repair Information Company, LLC.
Page 3294 of 4133
and therefore forms a complete unit.
The heater housing distributes the air which is required to ventilate the vehicle interior to the relevant air ducts
and air outlets depending on the temperature desired in the interior.
The air ducting depends on various operating conditions such as:
Heating
No heating
Fresh air mode
Recirculated air mode
FRESH AIR/RECIRCULATED AIR FLAP, LOCATION - GF83.20-P-2104-01GH
The fresh air/recirculated air flap (1) is located at the top of the heater/A/C housing.
Fig. 40: Identifying Fresh Air/Recirculated Air Flap
FRESH AIR/RECIRCULATED AIR FLAP, FUNCTION - GF83.20-P-2104-02GH
Function
The fresh air/recirculated air flap is actuated by the fresh air/ recirculated air flap actuator (M2/5).
Fresh air mode
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
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The fresh air/recirculated air flap shuts off the supply of recirculated air.
Fresh air is drawn in.
Recirculation mode
The fresh air/recirculated air flap shuts off the supply of fresh air. Air is drawn in from the passenger
compartment.
HEATER CORE, LOCATION/PURPOSE/FUNCTION - GF83.20-P-2108GC
MODEL 163, 168
HEATING WATER CIRCULATION PUMP, LOCATION/TASK/FUNCTION - GF83.20-P-2109GI
MODEL 163 as of 1.9.01 with code (580a) Automatic air conditioning
Fig. 41: Identifying Heating Water Circulation Pump
Heater core,
locationModel 168GF83.20-P-
2101-02GC
Model 163GF83.20-P-
2101-02GH
Heater core,
purposeThe heater core serves for heating up the air flowing through on the way
to the various defroster, ventilation and heating nozzles in the vehicle
passenger compartment.
Heater core,
function GF83.20-P-
2101-01GC
Heating water
circulation pump,
positionThe heating water circulation pump (M13) is located at the front
right in the engine compartment next to the coolant compensating
reservoir.
Heating water
circulation pump
taskThe heating water circulation pump (M13) serves to maintain a
constant flow of hot water through the heat exchanger in the event of
low engine speeds and residual engine heat utilization.
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
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Page 3296 of 4133
HEATER HOUSING POSITION/TASK/FUNCTION - GF83.20-P-2110GC
MODEL 163 up to 31.8.01
168 up to except CODE (580) Air conditioning or Tempmatic for USA
Shown on model 168 as of 1.03.01
Fig. 42: Identifying Heater Housing
- Shown On Model 168 As Of 1.03.01
FRESH AIR/RECIRCULATED AIR FLAP, LOCATION/PURPOSE/FUNCTION - GF83.20-P-2111GC
MODEL 163, 168
Heating water
circulation pump
function
GF83.20-P-
2102-01GI
Heater housing
positionThe heater housing (1) is located beneath the instrument
panel.
Model 168 up to 28.02.01GF83.20-P-2103-
01GC
Model 163GF83.20-P-2103-
01GH
Heater housing task GF83.20-P-2103-
03GC
Heater housing
functionModel 168GF83.20-P-2103-
02GC
Model 163GF83.20-P-2103-
02GH
2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 52 © 2006 Mitchell Repair Information Company, LLC.