MERCEDES-BENZ ML350 1997 Complete Repair Manual

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.

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.

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.

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
me
Saturday, October 02, 2010 3:23:15 PMPage 50 © 2006 Mitchell Repair Information Company, LLC.

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
me
Saturday, October 02, 2010 3:23:15 PMPage 51 © 2006 Mitchell Repair Information Company, LLC.

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.

BLOWER SWITCH, LOCATION - GF83.25-P-2100-01GH
Heater depiction
The blower switch (1) is located in the heater control unit.
Fig. 43: Identifying Blower Switch On Heater Control Unit

BLOWER SWITCH, FUNCTION - GF83.25-P-2100-02GC
Function
Depending on the setting of the blower switch, the current is guided via sliding contacts onto a contact plate,
and from there to the relevant series resistor assembly resistor for the set blower level.
On actuation of the starter, the control voltage for the blower (M2) is switched off at the control unit via
terminal 15x.
Model 168 as of 1.03.01
Blower level 4 is implemented by bridging two contact decks.
As a result of the design of the contact plate, the re-activation of
blower level 1 --> blower level 2 and
Fresh air/recirculated air
flap, locationModel 168GF83.20-P-2104-
01GC
Model 163GF83.20-P-
2104-01GH
Fresh air/recirculated air
flap, purposeThe fresh air/recirculated air flap switches the system
over from fresh air to recirculated air.
Fresh air/recirculated air
flap, functionModel 168GF83.20-P-2104-
02GC
Model 163GF83.20-P-
2104-02GH

2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 53 © 2006 Mitchell Repair Information Company, LLC.

blower level 2 --> blower level 3
may lead to an increase in the speed of the blower motor due to the short-term bridging of two contact plates
(intermediate setting).
BLOWER SWITCH, LOCATION/TASK/DESIGN/FUNCTION - GF83.25-P-2100GC
MODEL 163 up to 31.8.01 168
Shown on model 168 with heating as of 01.03.01
Fig. 44: Identifying Blower Switch (Model 168 With Heating As Of 01.03.01)

BLOWER SWITCH, LOCATION/TASK/DESIGN/FUNCTION - GF83.25-P-2100GI
MODEL 163 as of 1.9.01 with code (580a) Automatic air conditioning
Blower switch,
locationThe blower switch (N119s3) is located on the left in the heater
push-button control module.
Model 168 up to 28.02.01GF83.25-P-2100-
01GC
Model 163GF83.25-P-2100-
01GH
Blower switch,
taskThe blower switch activates several blower stages in fresh air
and recirculating air mode.
Blower switch
designThe blower switch is designed as a multi-level rotary switch with
an axis and wiper contact.
Blower switch,
function GF83.25-P-2100-
02GC

2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 54 © 2006 Mitchell Repair Information Company, LLC.

Fig. 45: Identifying Blower Switch - Model 163 As Of 1.9.01 With Code (580a Automatic Air
Conditioning
AIR DISTRIBUTION SWITCH, FUNCTION - GF83.25-P-2101-01GH
Function
Turning the air distribution switch causes two wire cables to move the air distribution flaps, in order to route air
through the air distribution system to the air vents. The air vents are:
defroster vents for windshield/side windows
center air vents
lower air vents
There are 12 possible indented positions for air distribution.
AIR DISTRIBUTION SWITCH, FUNCTION - GF83.25-P-2101-01GI
Function
The air distribution can be set manually or automatically:
Manual
Turning the air distribution switch

Blower
switch,
location
The blower switch (1) is located on left in the AAC push-button control module (N22).
Blower
switch, taskThe blower switch (1) activates several blower stages in fresh air and recirculating air
mode.
Blower
switch designThe blower switch (1) is equipped with a rotary ring with which the blower levels can be
set. The LEDs in the rotary ring display the set blower level.

Blower
switch,
functionThe blower switch (1) sets the control voltage for the blower regulator in 6 stages and 5
intermediate settings via the push-button control module, depending on the setting. This
facilitates blower speed control of 0 -100 %.


2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 55 © 2006 Mitchell Repair Information Company, LLC.

Automatic
Pressing the Auto button ( )
Turning the air distribution switch on the AAC push-button control modul e (N22) actuates the various air
distribution actuators via air conditioner bus.
The following basic settings for air distribution are provided:
 Air flow from center and side vents
 Air flow at center, side,
footwell and defroster vents
 Air outlet at the center, side and defroster vents
 Air flow at center, side and footwell vents
Apart from the 4 listed basic settings, a furt her 8 intermediate settings can be selected.
AIR DISTRIBUTION SWITCH, LOCATION - GF83.25-P-2101-02GH
Heater depiction
The air distribution switch (3) is loca ted in the heater control unit (S98).
Fig. 46: Identifying Ai r Distribution Switch

AIR DISTRIBUTION SWITCH , LOCATION/TASK/DESIGN/F UNCTION - GF83.25-P-2101GH
MODEL 163 up to 31.8.01
Air distribution
switch, location GF83.25-P-
2101-02GH
Air distribution
switch, taskThe air distribution switch regulates the flow of air through the air
distribution system to the air vent s for ventilation of the passenger
compartment.


2001 Mercedes-Benz ML320
1998-2005 HVAC Climate Control - 163 Chassis
me
Saturday, October 02, 2010 3:23:15 PMPage 56 © 2006 Mitchell Repair Information Company, LLC.