| Pressure gauges may be used to carry out the following checking and measuring work: |
| A - measuring pressure and temperature in the refrigerant gas loop: |
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| The high pressure gauge can be used to measure the pressure and temperature that spread evenly, with the air conditioning turned on, from the compressor outlet to the throttle or expansion valve, through the condenser. |
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| The low pressure gauge can be used to measure pressure and temperature that spread evenly, with the air conditioning turned on, from the throttling area or expansion valve to the compressor input, through the evaporator. |
Note | The pressure / temperature ratio indicated on the pressure gauges only exists in sections in which the refrigerant gas loop agent is in its liquid or vapor state, but not in sections in which it is in its gaseous state. In its gaseous state, the temperature is near 10 ºC to 30 ºC higher than that shown by the pressure gauge. |
| B - Refrigerant gas sample in a closed container: |
| A given closed container, or the refrigerant gas loop, contains R134a if the temperature indicated by the pressure gauge corresponds to the refrigerant gas temperature (the inert liquid is taken to room temperature). |
| A given closed tank, or the refrigerant gas loop when turned off, is empty when the temperature indicated by the pressure gauge is lower than the refrigerant gas temperature. |
Note | The pressure / temperature ratio indicated by the pressure gauge is no longer valid if there is no liquid and the pressure is obtained through the action of vapor. |
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