Mercedes-Benz ML320. Service manual - part 664

 

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Mercedes-Benz ML320. Service manual - part 664

 

 

HEATER CIRCUIT FUNCTION - GF83.20-P-2003GH 

MODEL 163  

Fig. 33: Identifying Heater Circuit Function 

Function  

The coolant pump (5) pumps cold coolant through the engine. The coolant absorbs the engine's heat and 
becomes heated. The heated coolant is then conducted through the heat exchanger (2). The air blowing by the 
heat exchanger (2) is heated and conducted into the vehicle interior. 

The coolant is routed over the coolant return (A) and the heating water circulation pump (6) back to the coolant 
pump (5). 

By far the greater percentage of the coolant does not flow through the heat exchanger (2), but from the engine to 
the coolant thermostat (4). Depending on the water temperature, this conducts the water through the radiator (3) 
or directly to the coolant pump (5). 

HEATER CONTROLS, FUNCTION - GF83.20-P-2004GH 

  Heater housing position/task/function

  GF83.20-P-2110GC

  Heating system heat exchanger, location/ purpose/function

 

GF83.20-P-2108GC

  Heater water circulation pump, location/task/ function

as of 1.09.01 GF83.20-P-2109GI

 

2001 Mercedes-Benz ML320 

1998-2005 HVAC Climate Control - 163 Chassis

  

me 

 

Model 163 up to 31.8.01  

The following components are integrated into the heater control unit (S98): 

Blower switch (1): with 0 setting and 4 levels. 

 The blower switch (1) is not available as an individual part. 

Temperature selector wheel (2): with the "Blue", non-heating setting and the continuously variable heater 
setting. 

Air distribution switch (3): with the settings: Defroster vents, footwell, center plane and intermediate settings. 

Recirculation switch (

 ): Functions if diode is illuminated. 

Fig. 34: Identifying Blower Switch, Selector Wheel And Air Distribution Switch On Heater Control Unit 

HEATER CORE, FUNCTION - GF83.20-P-2101-01GC 

Function  

The heater coolant flows through the heater core. The heat is conducted to the outside by the aluminum tubes 
and fins. 

This heats up the air flowing through on the way to the various defroster, vent and heater nozzles in the vehicle 
passenger compartment. 

HEATING SYSTEM HEAT EXCHANGER, LOCATION - GF83.20-P-2101-02GH 

The heater core (1) is located behind the instrument panel in the heater/ A/C housing. 

  Blower switch, location/task/design/function

  GF83.25-P-2100GC

  Air distribution switch, location/task/design/ function

  GF83.25-P-2101GH

  Temperature selector wheel, location/task/ design/function

  GF83.25-P-2102GC

  Air recirculation switch, location/task/design/ function

  GF83.10-P-2117GH

 

2001 Mercedes-Benz ML320 

1998-2005 HVAC Climate Control - 163 Chassis

  

me 

 

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 

 

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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