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14.1.1. Relationship between the condition of the air conditioner and pressure and electric
current
• Carry out the measurements of pressure, electric current, and temperature fifteen minutes after an operation is started.
14.1.2. Diagnosis methods of a malfunction of a compressor and 4-Way Valve
Cooling Mode Heating Mode
Low Pressure High Pressure
Electric current
during operating
Low Pressure High Pressure
Electric current
during operating
Condition of the air
conditioner
Insufficient refrigerant
(gas leakage)
Clogged capillary tube
or Strainer
Short circuit in the
indoor unit
Heat radiation deficiency
of the outdoor unit
Inefficient compression
Nature of fault Symptom
Insufficient compressing of a compressor
• Electric current during operation becomes approximately 20% lower than the normal value.
• The discharge tube of the compressor becomes abnormally hot (normally 70 to 90°C).
• The difference between high pressure and low pressure becomes almost zero.
Locker compressor
• Electric current reaches a high level abnormally, and the value exceeds the limit of an
ammeter. In some cases, a breaker turns off.
• The compressor has a humming sound.
Insufficient switches of the 4-way valve
• Electric current during operation becomes approximately 80% lower than the normal value.
• The temperature different between from the discharge tube to the 4-way valve and from
suction tube to the 4-way valve becomes almost zero.
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