Volkswagen Golf / Golf GTI / Jetta. Manual — part 978

87-119

6 - Receiver

drier

7 - Sight

glass

If

equipped

8 - High

pressure
service
valve

9

-

Expansion
valve

A/C refrigerant system, servicing

13/2/2005

87-120

Pressure and temperature specifications

Refer to pages

Page 87-118

and

Page 87-119

for component identification.

Component

Refrigerant

state

Approximate

pressure (bar/psi)

Approximate
temperature

1 - Evaporator, inlet to
outlet

Vapor to Gas

-7 C (19 F)

2)

2 - Low pressure
service valve

Gas

1.2 bar (17.4 psi)

1)

-1 C (30 F)

3 - Compressor, low
pressure side

Gas

4 - Compressor, high
pressure side

Gas

65 C (149 F)

5 - Condenser

Gas

to Vapor

55 C (131 F) at

outlet

to Liquid

14 bar (203 psi)

6 - Receiver drier

Liquid

7 - Sight glass (if
equipped)

Liquid

55 C (131 F)

8 - High pressure
service valve

Liquid

9 - Expansion valve

Liquid to

Vapor

Inlet: 14 bar (203 psi)

Outlet: 1.2 bar (17.4

psi)

Inlet: 55 C (131

F)

Outlet: -7 C (19

F)

1)

Pressure maintained in the refrigerant system by the variable displacement

compressor despite variables in temperature, load and engine speeds (RPM).

2)

Temperature maintained in the refrigerant system by the variable displacement

compressor despite variables in temperature, load and engine speeds (RPM).

A/C refrigerant system, servicing

13/2/2005

87-121

A/C refrigerant system, testing with
pressure gauges

Due to the constant temperature/pressure

relationship of refrigerant R-134a,
approximate high-side system temperature
can be determined based on system
pressure.

Pressure gauges may have one or more

temperature scales in addition to the
pressure scale. Since various refrigerants
have different temperature/pressure
relationships, each gauge is specific for a
particular refrigerant.

Measuring pressure and temperature in a

"switched-on" refrigerant system

Use the A/C refrigerant high-pressure gauge

to measure high pressure between the
compressor and restrictor (including
condenser) with the A/C switched on.

Use the A/C refrigerant low-pressure gauge

to measure low pressure between the
restrictor and the compressor inlet (including
evaporator) with the A/C switched on.

The temperature displays of the low- and

high-pressure gauges apply only to a portion
of the low- and high-pressure sides. The low-
pressure gauge displays approximate
temperature between the restrictor and
evaporator outlet. The high-pressure gauge
displays approximate temperature between
the compressor outlet and restrictor.

A/C refrigerant system, servicing

13/2/2005

87-122

Note:

The temperature/pressure relationship only

holds true when the refrigerant system
contains liquid and vapor, but not when it
contains only gas. In the gaseous state, the
temperature is approx. 10-30 C (18-54 F)
higher than indicated on the pressure gauge.

Measuring pressure and temperature in a

closed container or "switched-off"
refrigerant system

Due to the constant temperature/pressure

relationship of R-12 and R-134a,
approximate temperaturein a closed
container or in a switched-off A/C system
can be determined based on its pressure.

If the temperature displayed on a gauge is

lower than the actual temperature of the
refrigerant, the refrigerant container or
system is empty (discharged).

Note:

The temperature/pressure relationship only

holds true when the refrigerant system
contains liquid and vapor, but not when it
contains only gas. In the gaseous state, the
temperature is approx. 10-30 C (18-54 F)
higher than indicated on the pressure gauge.

A/C refrigerant system, servicing

13/2/2005