Mitsubishi Electric PQHY-P72TYHMU-A Service Handbook page 307

[ IX Troubleshooting ]
Both for MA remote controller and ME remote controller
1. Phenomena
Although cooling operation starts with the normal remote controller display, the capacity is not enough
(1) Cause, check method and remedy
1. Compressor frequency does not rise sufficiently.
ŒFaulty detection of pressure sensor.
ŒProtection works and compressor frequency does
not rise due to high discharge temperature
ŒProtection works and compressor frequency does
not rise due to high pressure
ŒPressure drops excessively.
2. Indoor unit LEV malfunction
ŒInsufficient refrigerant flows due to LEV malfunc-
tion (not enough opening) or protection works and
compressor frequency does not rise due to pres-
sure drop.
ŒRefrigerant leak from LEV on the stopping unit
causes refrigerant shortage on the running unit.
HWE09080
Cause
- 298 -
Check method and remedy
(1) Check pressure difference between the detected
pressure by the pressure sensor and the actual
pressure with self-diagnosis LED.
-> If the accurate pressure is not detected, check
the pressure sensor. (Refer to the page on Trouble-
shooting of Pressure Sensor).
Note: Lower inlet pressure by the low pressure sensor
than the actual pressure causes insufficient capac-
ity.
SW1 setting
High pressure sensor
SW1
ON
Low pressure sensor
SW1
ON
(2) Check temperature difference between the evapo-
rating temperature (Te) and the target evaporating
temperature (Tem) with self-diagnosis LED.
Note: Higher Te than Tem causes insufficient capacity.
SW1 setting
Evaporating temperature Te
SW1
ON
Target evaporating temperature Tem
SW1
ON
Note: Protection works and compressor frequency does
not rise even at higher Te than Tem due to high dis-
charge temperature and high pressure.
At high discharge temperature:
Refer to 1102.(page 231)
At high pressure:
Refer to 1302.(page 233)
Refer to the page of LEV troubleshooting ([4] -4-
).(page 310)
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