Volkswagen Golf / Golf GTI / Jetta. Manual - part 1002

  

  

 

water (ice-up safeguard).

Coolant FC (Fan Control) Control Module J293 

Note: 

- There are various construction styles. 

This control module switches on and off the A/C clutch and 
therefore the A/C compressor. It switches the coolant fans 
and (in vehicles with High Pressure Sensor G65 or A/C 
Pressure/temperature Sensor G395 ) calculates the 
pressure in the refrigerant circuit. 

A/C Evaporator Temperature Switch E33 

 

Function:

A/C Evaporator Temperature Switch E33 determines the 
temperature between the evaporator cooling ribs. It 
prevents the possibility of ice build-up between evaporator 
cooling ribs by interrupting the current supply to A/C clutch 
of A/C compressor when temperature at the cooling ribs 
sinks to the freezing point for air moisture. 

Insertion depth of the sensor tube is marked or listed in the 
repair manual 

 
 

 Repair Manual, Heating & Air Conditioning, Repair 

Group 87 , 

General information on refrigerant circuit

13/2/2005

  

. 

Note: 

- Installed in VW vehicles with A/C compressor driven via 
ribbed belt 

Evaporator Vent Temperature Sensor G263 

 

Function:

Evaporator Vent Temperature Sensor G263 determines 
temperature behind the evaporator. This value is sent to 
A/C system control module and serves as a reference 
signal for A/C compressor regulation. 

Pressures and temperatures in refrigerant 
circuit

 

Warning!  

 

When performing work on refrigerant circuit, observe 
all generally applicable safety precautions and 
pressure vessel regulations.

 

The pressures and temperatures in refrigerant circuit are 
dependent on the current operating conditions (e.g. engine 
RPM, coolant fan stage 1, 2 or 3, engine temperature, A/C 
compressor on or off) as well as on the effects of ambient 
influences (e.g. ambient temperature, humidity, requested 
cooling output).

In vehicles with A/C Compressor Regulator Valve N280 , 
pressure is modified on the low pressure side by the valve. 

For this reason, values indicated in the following table are 
valid only as reference points. They are attained at an 
engine speed of 1500 to 2000 RPM and an ambient 
temperature of 20   C after about 20 minutes. 

 

The connections for the pressure gauge set intended for 
the pressure measurement are indicated on the vehicle 
specific refrigerant circuit.

 
 

 Repair Manual, Heating & Air Conditioning, Repair 

Group 87 , 

At 20   C with the engine not running, the pressure in the 

General information on refrigerant circuit

13/2/2005

 

 

refrigerant circuit is 4.7 bar 

 

00-1, Vapor pressure table 

for refrigerant R134a

 . 

Refrigerant circuit with expansion valve

 

 

A- Low pressure side of refrigerant circuit.

 

B- High pressure side of refrigerant 
circuit.

Component

Aggregate state of 

refrigerant

Pressure (bar 

positive pressure)

Temperature in 

degrees Celsius

- 1 - Evaporator, from input 
to output 

Vapor

approx. 1.2 bar 

1)

 

approx. -7   C 

2)

 

 

 

(approx. 1.8 bar) 

3)

 

(approx. -1   C) 

3)

 

- 2 - A/C compressor A- 
side 

Gas

approx. 1.2 bar 

1)

 

approx. -1   C 

 

 

(approx. 1.8 bar) 

3)

 

(approx. +1   C) 

3)

 

- 3 - A/C compressor B- 
side 

Gas

approx. 14 bar

approx. +65   C 

- 4 - Condenser 

Gas, vapor, liquid

approx. 14 bar

approx. +55   C at 
outlet 

- 5 - Receiver 

liquid

approx. 14 bar

approx. +55   C 

- 6 - Charging and 
evacuating valve B- side 

liquid

approx. 14 bar

approx. +55   C 

- 7 - Expansion valve 

liquid, released as 
vapor

approx. 14 bar

approx.+ 55   C, 
reduced to -7   C 

- 8 - Charging and 
evacuating valve A- side 

Gas

approx. 1.2 bar 

1)

 

approx. -7   C 

2)

 

 

 

(approx. 1.8 bar) 

3)

 

(approx. -1   C) 

3)

 

1)

 Pressure in refrigerant circuits is maintained at approx. 2 

bar, regulated by A/C compressor, even though heat 
transfer changes and engine speeds vary. However, this 
applies only within the performance range of the A/C 
compressor; if the performance limits of the A/C 
compressor are exceeded, the pressure increases 

 

00-7, 

Pressures, checking on vehicles

 . 

2)

 Within the control range of the A/C compressor, 

temperature in the refrigerant circuits is maintained, 
regulated by A/C compressor, even though heat transfer 
changes and engine speeds vary. However, this applies 
only within the performance range of the A/C compressor; if 
the performance limits of the A/C compressor are 
exceeded, the temperature increases 

 

00-7, Pressures, 

General information on refrigerant circuit

13/2/2005

 

 

checking on vehicles

 . 

3)

Measured values for A/C systems with two evaporators  

Note: 

- A/C compressors which do not regulate their performance 
are switched off by the respective control module via the 
A/C Compressor Regulator Valve N280 at an evaporator 
temperature below 0   C. 

- In vehicles with A/C Compressor Regulator Valve N280 , 
pressure is modified on the low pressure side by the valve. 

Refrigerant circuit with restrictor and 
reservoir

 

 

Arrows point in direction of refrigerant 
flow.

 

A- Low pressure side of refrigerant circuit.

 

B- High pressure side of refrigerant 
circuit.

Component

Aggregate state of 

refrigerant

Pressure (bar positive 

pressure)

Temperature in degrees 

Celsius

- 1 - A/C 
compressor B- side 

Gas

up to 20 bar

up to + 70   C 

- 2 - Condenser 

From gas to vapor 
to liquid

up to 20 bar

up to + 70   C 

- 3 - Restrictor 

From liquid to 
vapor

B-side up to 20 bar, A-
side greater than 1.5 bar

B-side up to +60   C, A-side 
warmer than -4   C 

- 4 - Evaporator 

From vapor to gas

Greater than 1.5 bar

Warmer than -4   C 

- 5 - Reservoir 

Gas

 

 

- 6 - A/C 
compressor A- side 

Gas

 

 

Pressures on A-side are maintained at approx. 2 bar by the 
"regulating" A/C compressor also at various engine speeds. 
However, this applies only within the performance range of 
the A/C compressor; if the performance limits of the A/C 
compressor are exceeded 

 

00-7, Pressures, checking on 

vehicles

 . 

Note: 

- In vehicles with A/C Compressor Regulator Valve N280 , 

General information on refrigerant circuit

13/2/2005