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