Mercedes-Benz ML320. Manual - part 686

Fig. 110: Identifying Refrigerant Compressor Control Valve, Function (1 Of 2) 

Variable volume control in partial load range  

(e.g. at low ambient temperature or low cooling capacity requirement) 

Essentially, the cooling output is dependent on the intake pressure, i.e. if the suction pressure (Ps) drops below 
the diaphragm pressure (Ps1) in the refrigerant compressor control valve and the regulating current is reduced at 
the same time, then the passage from high pressure (Pd) to crankcase pressure (Pc) is released by the control 
plunger (2) in the refrigerant compressor control valve. As a result, refrigerant flows from the high pressure side 
into the crankcase which results in an increase in crankcase pressure (Pc). 

The sum of the forces on the left-hand side, resulting from the crankcase pressure (Pc), the return force 
(centrifugal force) of the swash plate and the spring return force thus becomes greater than total piston forces. 
The swash plate moves into a vertical position, which causes a reduction in piston travel and replacement 
volume. 

In addition, a regulation of the cooling output takes place as a function of the air humidity, i.e. at high air 
humidity there is an external actuation of the control valve, achieving a post-regulation of the cooling output 
(preventing fogging up of the windows). 

The refrigerant compressor is automatically switched off at a volumetric flow of less than 5 cm

3

.

 

 

2001 Mercedes-Benz ML320 

1998-2005 HVAC Climate Control - 163 Chassis

  

me 

 

Fig. 111: Identifying Refrigerant Compressor Control Valve, Function (2 Of 2) 

Control at max. swept volume  

(e.g. at higher ambient temperature or higher cooling capacity requirement) 

If the suction pressure (Ps) rises above the diaphragm pressure (Ps1) in the refrigerant compressor control valve 
and the control current is increased at the same time, in the refrigerant compressor control valve the passage - 
high pressure (Pd) to crankcase pressure (Pc) - is closed by the control plunger (2). The crankcase pressure (Pc) 
drops, as no refrigerant flows from the high pressure side into the crankcase via the refrigerant compressor 
control valve. 

In the long-term the bypass (1) sets up a pressure compensation between the suction pressure (Ps) and crankcase 
pressure (Pc), i.e. the sum of the reaction forces on the left side, resulting from the crankcase pressure (Pc), 
return force of the swash plate (centrifugal force) and the spring return force, is therefore smaller than the sum 
of the piston forces. The swash plate angle extends to beyond the "0-position ", i.e. the inclined position 
increases continuously to the swash plate's mechanical limit stop at the stop plate. The piston stroke increases 
linear to the swash plate's inclination till it reaches max. volumetric flow. 

CONTROL VALVE, LOCATION/TASK/FUNCTION - GF83.55-P-2102P 

ENGINE 111, 112, 113, 271, 272, 611, 612, 642, 646 in MODEL 203.0 /2 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  

 

2001 Mercedes-Benz ML320 

1998-2005 HVAC Climate Control - 163 Chassis

  

me 

 

ENGINE 111, 112, 271, 272, 611, 612, 646 in MODEL 203.7 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  

ENGINE 112.942 /970, 113.942 /965 /981, 612.963, 628.963 in MODEL 163 as of 1.9.01 with CODE (580) 
Automatic air conditioning  

ENGINE 112, 113, 271, 272, 273, 612, 642, 646 in MODEL 209.3  

ENGINE 112, 113, 271, 272, 273, 642 in MODEL 209.4  

Shown on model 203  

Fig. 112: Identifying Refrigerant Compressor Control Valve And Compressor - Shown On Model 203 

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. 

 

Refrigerant compressor 
control valve, position

The refrigerant compressor control valve (1) is located on the 
refrigerant compressor (A9).

 

 

Refrigerant compressor 
control valve, task

The refrigerant compressor control valve (1) regulates the swept 
volume of the refrigerant compressor (A9) dependent upon the 
refrigerant capacity requirement.

 

 

Refrigerant compressor 
control valve, function

 

GF83.55-P-
2102-02P

 

2001 Mercedes-Benz ML320 

1998-2005 HVAC Climate Control - 163 Chassis

  

me 

 

Fig. 113: Identifying Belt Pulley, Function - Function Under Normal Operating Conditions 

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. 

Fig. 114: Identifying Belt Pulley, Function - Function Of Refrigerant Compressor Lock Up 

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. 

 

2001 Mercedes-Benz ML320 

1998-2005 HVAC Climate Control - 163 Chassis

  

me