Mercedes-Benz ML320. Service manual - part 665

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 

 

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 

 

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 

 

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