Mercedes-Benz ML320. Service manual — part 684

Fig. 101: Identifying Refrigerant Compressor, Function - (2 Of 2)

Function

5% power (III)

If the engine speed is high or the thermal load is low, this results in a constantly low manifold air pressure C
which keeps the control valve open.

There is a flow from the high-pressure side A to the crankcase. The pressure in the crankcase B reaches a peak.
Consequently, the swash plate is forced into a position in which only a minimum power is possible. The angle
between the vertical and the swash plate is at its smallest. This results in a small stroke.

Power from 5% to 100% output ( IV )

If the conditions change again in that the thermal load increases or the engine speed drops, the manifold air
pressure C increases. There is now no longer any flow between the rear opening and the crankcase.

Due to the uniform flow from the crankcase to the inlet opening through the transfer duct, the high pressure A
reaches almost the same level as the manifold air pressure C . Consequently, the swash plate angle increases
and therefore the power increases until it reaches a maximum.

REFRIGERANT COMPRESSOR, FUNCTION - GF83.55-P-2100-02P

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me

Fig. 102: Identifying Refrigerant Compressor Components

Function

The rotary movement of the belt pulley (1) is transmitted via the refrigerant compressor shaft (13) to the stop
plate (12), which is permanently fastened to the refrigerant compressor shaft (13) by way of a press fit.

The rotation of the stop plate (12) is transmitted to the swash plate (4) by means of a hinged mechanism.

Conversion of the swash plate's (4) rotary motion into the oscillating motion of the seven pistons (6) takes place
via two sliding shoes each (11).

The evaporation tank on the pressure side (5) and evaporation tank on the suction side (7) reduce gas pulsation
in the refrigerant compressor by providing for uniform refrigerant flow. This helps to prevent noise in the
compression process

Volume control

The refrigerant compressor control valve (8) has a corresponding control current applied to it to match the
output requested. This in turn enables the compression volume to be regulated between 2 and 100 %.

The position of the swash plate (4) is determined through monitoring, processing and evaluation of the
following automatic air conditioning controlled variables:



Pressure in the crankcase (2) of the refrigerant compressor

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me



Diaphragm pressure in the refrigerant compressor control valve (8) (approx. 2 bar)



Suction pressure of refrigerant compressor

The change in suction pressure which is dependent on the control current on the refrigerant compressor control
valve (8) induces a change of pressure in the crankcase (2) and thus a corresponding adjustment of the swash
plate (4).

Automatic air conditioning (AAC [KLA]) OFF

If the automatic air conditioning is regulated or manually switched off, the refrigerant compressor control valve
(8) is completely opened. Refrigerant flows unobstructed over the high pressure side into the crankcase (2). This
in turn leads to a rapid pressure rise in the crankcase (2). The coil body (10), for closing the refrigerant
compressor, is displaced here to the right against the valve plate (9) and thus stops the flow of refrigerant over
the intake side.

Refrigerant compressor lubrication when automatic air conditioning switched off

An internal lubrication circuit ensures the lubrication supply for all moving parts.

Lubrication is ensured at a minimum refrigerant compressor volumetric flow by means of two valves being
regulated. In doing so, the refrigerant is transported together with the compressor oil located in the crankcase
(2) over the bored refrigerant compressor shaft (13). The mixture enters the cylinder housing, where it is
compressed and then pumped into the refrigerant circuit.

REFRIGERANT COMPRESSOR, DESIGN - GF83.55-P-2100-03P

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me

Fig. 103: Identifying Refrigerant Compressor Components

REFRIGERANT COMPRESSOR, LOCATION/TASK/DESIGN/FUNCTION - GF83.55-P-2100GH

ENGINES 111.977, 112.942, 113.942/981, 612.963 in MODEL 163 up to 31.08.01 with CODE (580) Air
conditioning or Tempmatic for USA refrigerant compressor 7SB16C

Design

Refrigerant compressor 7SB16C

Fig. 104: Identifying Refrigerant Compressor 7SB16C Components

REFRIGERANT COMPRESSOR, LOCATION/TASK/DESIGN/FUNCTION - GF83.55-P-2100P

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

Refrigerant compressor,
position

GF83.55-P-2100-
01GH

Refrigerant compressor,
task

The refrigerant compressor (A9) is responsible for induction
and compression of the refrigerant.

Refrigerant compressor,
function

GF83.55-P-2100-
02A

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me