Volkswagen Touran Service Manual: Pressure Gauge, Tests and Measurements
| Indicators on pressure gauge |
| 1 - |
Temperature scale for refrigerant R134a CF3CH2F or
CH2FCF3. |
| The pressure gauge may have one or more temperature scales
next to the pressure scale. The R134a scale values are allocated
respectively in the vapor pressure table. Since various
refrigerants create different vapor pressures at the same
temperature, each temperature scale is identified for the
respective refrigerant. |
| a Pressure and temperature measurement at refrigerant
circuit |
| High pressure gauge measures pressure and temperature, which
expand uniformly from outlet of A/C compressor via the condenser
up to constriction (restrictor, or expansion valve) with A/C
system switched on. |
| Low pressure gauge measures pressure and temperature, which
expand uniformly from constriction (restrictor, or expansion
valve) via evaporator up to input of A/C compressor with A/C
system switched on. |
 Note
| The relationship between pressure and temperature indicated
on the gauges only exists in a refrigerant circuit that contains
liquid or vapor, but not gas. In a gaseous state, the
temperature is approximately 10 C (50 F) to 30 C (86 F)
higher than indicated on the gauge. |
| b Verification of refrigerant in a closed container |
| Refrigerant R134a is present in a closed vessel or in a
refrigerant circuit when the temperature indicator on the gauge
matches the refrigerant temperature (the temperature of standing
fluid is equal to the outside temperature). |
| A closed vessel or a refrigerant circuit that has been
switched off is empty when the temperature indicated on the
gauge is below the temperature of the refrigerant. |
Note
| The relationship between pressure and temperature indicated
on the gauges no longer applies if no liquid is present and the
pressure is built up solely by gas. |
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Arrows point in direction of refrigerant flow.
A-Low pressure side of refrigerant circuit.
B-High pressure side of refrigerant circuit.
&nbs ...
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Refrigerant Circuit with Restrictor and Reservoir