| Pressure gauges permit the following test and measurement operations |
| Refrigerant circuit pressure and temperature measurements |
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| The high-pressure gauge measures the pressure and temperature propagated evenly from the air conditioner compressor outlet via the condenser to the constriction (restrictor or expansion valve) when the air conditioning system is switched on. |
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| The low-pressure gauge measures the pressure and temperature propagated evenly from the constriction (restrictor or expansion valve) via the evaporator to the inlet of the air conditioner compressor when the air conditioning system is switched on. |
Note | The relationship between pressure and temperature indicated on the pressure gauges only exists in a refrigerant circuit containing liquid or vapour, but not gas. In the gas state, the temperature is approx. 10 °C to 30 °C higher than the pressure gauge reading. |
| Detection of refrigerant in a closed vessel |
| Refrigerant R134a is present in a closed vessel or in the refrigerant circuit if the temperature indicated on the pressure gauge corresponds to the temperature of the refrigerant (standing liquid assumes ambient temperature). |
| A closed vessel or a deactivated refrigerant circuit is empty if the temperature indicated on the pressure gauge is below the temperature of the refrigerant. |
Note | The relationship between pressure and temperature indicated on the pressure gauges no longer applies if no liquid is present and the pressure is built up solely by gas. |
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