Mercedes-Benz ML320. Manual — part 679

Whenever the system is opened, the fluid reservoir should be replaced because of the water which has

collected there in the meantime.

EXPANSION VALVE, FUNCTION - GF83.40-P-2123-01GC

Function

When the refrigerant compressor is switched on the pressure in the evaporator drops, thereby causing the
diaphragm (1) to curve downwards. The control valve (3) follows the movement of the diaphragm and presses
the ball (4) out of its seating against the spring (5). The opened valve enables the refrigerant to be sprayed into
the evaporator.

As the diaphragm movement (1) is dependent on both the intake pressure and the temperature at the evaporator
outlet, only the specific quantity of refrigerant, as required for optimum vaporization, is injected.

Fig. 83: Identifying Expansion Valve Components

EXPANSION VALVE, LOCATION - GF83.40-P-2123-02GH

The expansion valve (1) is located on the right at the rear in the engine compartment next to the battery.

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me

Fig. 84: Locating Expansion Valve

EXPANSION VALVE, LOCATION/TASK/DESIGN/FUNCTION - GF83.40-P-2123GC

MODEL 163 up to 31.08.01, 168 with CODE (580) Air conditioning or Tempmatic for USA

MODEL 163 as of 01.09.01 with CODE (580a) Automatic air conditioning

Design

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me

Fig. 85: Identifying Expansion Valve Design

REFRIGERANT PRESSURE SENSOR, FUNCTION - GF83.40-P-2126-01GH

Function

Shutting off the refrigerant compressor

The refrigerant pressure sensor (B12) sends the current value to the All Activity Module (N10). The All
Activity Module (N10) compares this input information with stored values and actuates the refrigerant
compressor.

At the following values, the refrigerant compressor is switched on or off:



refrigerant pressure > 3 bar = refrigerant compressor ON



refrigerant pressure < 2 bar = refrigerant compressor OFF



refrigerant pressure < 26 bar = refrigerant compressor ON



refrigerant pressure > 30 bar = refrigerant compressor OFF

Cut-in of the auxiliary fan (engines 111.977 and 112.942)

The pressure value received from the refrigerant pressure sensor (B12) is recorded by the All Activity Module
(N10) and compared there with a stored value.

As of 12/99, the Extended Activity Module (EAM, N10/1) assumes this task from the All Activity Module
(N10).

At the following values, the auxiliary fan (M4m1, M4m2) is switched on or off:



refrigerant pressure > 16 bar = auxiliary fan ON



refrigerant pressure <12 bar = auxiliary fan OFF

Cut-in of the electric fan for engine/AC (engines 113.942/981 and 612.963)

The pressure value received from the refrigerant pressure sensor (B12) is recorded by the All Activity Module
(N10), sent to the control module integrated in the electric fan for engine/AC and compared there with a stored

Expansion valve,
location

Model 168

GF83.40-P-2123-
02GC

Model 163

GF83.40-P-2123-
02GH

Expansion valve, task

The expansion valve injects the liquid refrigerant into the
evaporator.

Expansion valve,
function

GF83.40-P-2123-
01GC

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me

value.

At the following values the electric fan for engine/AC (M4/7) is switched on or off:



refrigerant pressure > 20 bar = electric fan for engine/AC ON



refrigerant pressure <12 bar = electric fan for engine/AC OFF

REFRIGERANT PRESSURE SENSOR, LOCATION - GF83.40-P-2126-02GH

The refrigerant pressure sensor (B12) is located at the front left in the engine compartment at the high-pressure
line (8) between the refrigerant compressor (A9) and the capacitor (7).

Fig. 86: Identifying Refrigerant Pressure Sensor

DEFROSTER BUTTON, FUNCTION - GF83.40-P-2139-02GI

Function

Pressing the defroster button (

) initiates the defrost function.

Function feedback takes place by means of a yellow LED.

The defrost function works according to the following logic:



the heating power is regulated using the outside temperature



the entire air flow is directed at the windshield and the front side windows, and the defroster nozzles are

2001 Mercedes-Benz ML320

1998-2005 HVAC Climate Control - 163 Chassis

me