Volkswagen Golf Service & Repair Manual: Test and measurement work that can be performed using a pressure gauge
| Displays on the pressure gauge |
| 1 - |
Temperature scale for refrigerant R134a CF3–CH2F or
CH2F–CF3. |
| In addition to the pressure scale, the pressure gauges can
have one or more temperature scales. The scale values for R134a
are assigned according to the vapour pressure table. Because
different refrigerants have different vapour pressures at the
same temperature, each temperature scale is labelled for the
respective refrigerant. |
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Pressure gauges enable the following test and measurement work
| a – Pressure and temperature measurement in the refrigerant
circuit |
| The high-pressure gauge allows the pressure and temperature
to be measured with the air conditioning system switched on
irrespective of whether this is at the outlet of the air
conditioner compressor through the condenser up to the
restriction (restrictor or expansion valve). |
| The low-pressure gauge allows the pressure and temperature
to be measured with the air conditioning system switched on
irrespective of whether this is at the restriction (restrictor
or expansion valve) through the evaporator up to the inlet to
the air conditioner compressor. |
 Note
| The relationship between pressure and temperature shown on
the pressure gauge is valid only where the refrigerant in the
circuit is liquid or vapour, but not when it is gas. In the
gaseous state, the temperature is approx. 10°C to 30°C higher
than indicated on the pressure gauge. |
| b– Evidence of refrigerant in a closed container |
| Refrigerant R134a is present in a closed container or
refrigerant circuit if the temperature indicated on the pressure
gauge corresponds to the temperature of the refrigerant (the
temperature of a standing liquid stabilises at ambient
temperature). |
| A closed container or switched-off refrigerant circuit is
empty if the temperature indicated on the pressure gauge is
below the temperature of the refrigerant. |
Note
| The dependency between pressure and temperature described on
the pressure gauge no longer applies when there is no liquid and
the pressure is created by gas alone. |
|
Arrows show the direction of refrigerant flow.
A- low-pressure side of the refrigerant circuit.
B- high-pressure side of the refrigerant circuit.
...
At present, various manufacturers offer air conditioner
service devices on the market for evacuating, cleaning and
charging refrigerant in vehicle air conditioning sy ...
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Refrigerant circuit with restrictor and reservoir
Air conditioner service and recycling equipment