| Pressure gauges allow to carry out the following inspection and measurement work |
| Pressure and temperature measurement on the refrigerant circuit |
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| The high-pressure manometer measures the pressure and the temperature, which spreads evenly from the outlet of the AC compressor via the condensor up to the constriction (throttle or expansion valve) when the AC compressor is switched on. |
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| The low-pressure manometer measures the pressure and the temperature, which spreads evenly from the constriction (throttle or expansion valve) via the evaporator up to the inlet of the AC compressor. |
Note | The interdependence described on the pressure gauges, between pressure and temperature, only exists where liquid or vapour is contained in the refrigerant circuit, however not gas. In the gaseous condition, the temperature is around 10°C to 30°C higher than the pressure gauge indicates. |
| Evidence of refrigerants in a closed reservoir |
| In a closed reservoir or in the refrigerant circuit, the refrigerant R134a is present if the temperature reading of the pressure gauge corresponds to the temperature of the refrigerant (liquid is at ambient temperature). |
| A closed reservoir or a switched off refrigerant circuit is empty if the temperature reading of the pressure gauge lies below the temperature of the refrigerant. |
Note | The interdependence described on the pressure gauges, between pressure and temperature, does no longer exist if no liquid is contained and the pressure only builds up through gas. |
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