Beetle A/C systems: Information topic.

[NewBeetleMechanic]

A/C System Identification:

NOTE: Before carrying out any work on the A/C refrigerant system, refer to "A/C Refrigerant System, Safety Measures" See Service Precautions\Technician Safety Information

A/C refrigerant systems on New Beetle models are charged with refrigerant R-134a.
A label specifying refrigerant type may be located on the compressor or radiator support.

A/C refrigerant circuit with expansion valve and receiver drier



1 - Evaporator
2 - Expansion valve
3 - High pressure service valve
4 - - Sight glass (if equipped)
5 - Receiver drier
6 - Condenser
7 - Compressor

NOTE: Arrows indicate direction of refrigerant flow.

[NewBeetleMechanic]

Commercial designation
The following designations are used and appear on component Labels and factor tags:


•R-134a
•Tetrafluoroethane
•CH2F CF3
•H-KW 134a
•SUVA(R) 134a
•ARCTON(R) 134a
Color
Refrigerant R-134a is colorless and is invisible as a gas. R-134a when viewed through the sight glass may appear milky due to the mixture of refrigerant and lubricating oil (PAG oil).

Temperature/pressure relationship
R-134a in an enclosed container will have a specific temperature/ pressure relationship.



Temperature in °C (°F) Pressure in bar (psi)
-30 (-22) 0.0 (0.0)
-20 (-4) 0.3 (4.4)
-10 (14) 1.0 (14.5)
0 (32) 1.9 (275)
10 (50) 3.1 (45.0)
20 (68) 4.7 (68.2)
30 (86) 6.7 (97.2)
40 (104) 9.1 (132.0)
50 (122) 12.2 (177.0)
60 (140) 15.8 (229.2)
70 (158) 20.2 (293.0)

Refrigerant oil
A special Polyalkylene Glycol (PAG) synthetic oil is used in R-134a systems. This oil is NOT compatible with mineral based oils used in R-12 systems. Refer to Cautions and Warnings regarding proper oil usage see page 87-1.

Airborne properties
Escaped refrigerant gases are heavier than air and will gather first in low places, like under the car. R-134a refrigerant gas displaces oxygen and may cause suffocation in low areas of poor air circulation.

Refrigerant R-134a is not poisonous in any state (liquid or gas) and is sate when used properly.

Affects on plastic
Refrigerant R-134a will deteriorate some plastics. Therefore, when making system repairs, use only genuine VW replacement parts which are specified for use with R-134a refrigerant.

Affects on metal
In its pure state, refrigerant R-134a is chemically stable and will not attack iron, copper, brass or aluminum. However, the mixture of R-134a and PAG oil may deteriorate certain metals (copper). Therefore, when making system repairs, use only genuine WV replacement parts which are specified for use with R-134a refrigerant.

Water solubility
Liquid R-134a refrigerant will absorb only very minute quantities of moisture. However, R-134a vapor can absorb large amounts of moisture.

Flammability
R-34a refrigerant is not flammable

Refrigerant containers
DO NOT exceed maximum rated capacity of refrigerant container.

Leak detection
Use halogen leak detector Hitec H1400A-TEL or equivalent to check for R-134a system leaks. This tool can also be used to detect leaks in R-12 systems. Many currently available R-12 leak detectors cannot detect R-134a refrigerant leaks.

R-134a refrigerant oil
A special Polyalkylene Glycol (PAG) synthetic oil is used in R-134a systems. This oil is NOT compatible with mineral based oils used in H-12 systems.

[NewBeetleMechanic]

A/C refrigerant system pressures and temperatures, checking

The pressures and temperatures in the A/C system will vary depending on engine speed (RPM), coolant fan speed, engine coolant temperature, A/C clutch engagement, outside temperature, humidity, etc.

Pressure and temperature specifications are based on the following:

Engine speed (RPM) at 1500
Fresh air blower on high speed
A/C adjusted to Max. cooling

Pressure and temperature specifications, refer to "Pressure and Temperature Specifications"




1 - Evaporator
2 - Low pressure service valve
3 - Compressor, low pressure side
4 - Compressor, high pressure side
5 - Condenser
6 - Receiver drier

7 - Sight glass
If equipped

8 - High pressure service valve
9 - Expansion valve

[NewBeetleMechanic]

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.



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 temperature in 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 r6frigerant 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.

[NewBeetleMechanic]

NOTE: A/C evaporator temperature switch -E33- (if equipped) switches A/C compressor OFF only in special instances so evaporator does not ice up; variable displacement A/C compressor maintains temperature of 0 °C (32 °F ) in evaporator.

Test conditions


•A/C refrigerant system fully charged
•A/C clutch -N25- and compressor function OK
•Condenser and radiator clean and free of obstructions
•Air distribution can be adjusted properly
•Wiring OK as per wiring diagram
•Outside (ambient) temperature 20 °C-30 °C (68 °F-86 °F )
Checking


•Start engine.
•Set temperature control to maximum "cold".
•Press A/C button and select second blower speed.
•Adjust air distribution to instrument panel outlets.
•Insert thermometer into center instrument panel outlet.
•Raise engine speed to approximately 1500 RPM .
Specified result
With normal humidity and outside (ambient) temperature between 20-25 °C (68-77 °F ), system is sufficiently charged if air temperature from center instrument panel vent drops below 10 °C (50 °F ) within one minute .

For higher ambient temperatures and/or higher humidity, specified air temperature from center instrument panel vent can be slightly higher.