Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 319

[ IX Troubleshooting ]
(3) Both for MA remote controller and M-NET remote controller
Phenomena
1 Although cooling operation
starts with the normal remote
controller display, the capacity
is not enough
Cause
1. Compressor frequency does not
rise sufficiently.
Faulty detection of pressure
sensor.
Protection works and compres-
sor frequency does not rise due
to high discharge temperature
Protection works and compres-
sor frequency does not rise due
to high pressure
Pressure drops excessively.
2. Indoor unit LEV malfunction
Insufficient refrigerant flows due
to LEV malfunction (not enough
opening) or protection works and
compressor frequency does not
rise due to pressure drop.
Refrigerant leak from LEV on the
stopping unit causes refrigerant
shortage on the running unit.
3. RPM error of the outdoor unit FAN
Motor failure or board failure, or
airflow rate decrease due to clog-
ging of the heat exchanger
The fan is not properly controlled
as the outdoor temperature cannot
be precisely detected by the tem-
perature sensor.
The fan is not properly controlled
as the pressure cannot be precise-
ly detected by the pressure sen-
sor.
- 310 -
Check method and remedy
(1) Check pressure difference between the
detected pressure by the pressure sen-
sor and the actual pressure with self-di-
agnosis LED.
-> If the accurate pressure is not de-
tected, check the pressure sensor. (Re-
fer to the page on Troubleshooting of
Pressure Sensor).
Note: Lower inlet pressure by the low
pressure sensor than the actual
pressure causes insufficient ca-
pacity.
SW1 setting
High pressure sensor
1 2 3 4 5 6 7 8 9 10
ON
Low pressure sensor
1 2 3 4 5 6 7 8 9 10
ON
(2) Check temperature difference between
the evaporating temperature (Te) and
the target evaporating temperature
(Tem) with self-diagnosis LED.
Note: Higher Te than Tem causes in-
sufficient capacity.
SW1 setting
Evaporating temperature Te
1 2 3 4 5 6 7 8 9 10
ON
Target evaporating temperature Tem
1 2 3 4 5 6 7 8 9 10
ON
Note: Protection works and compressor
frequency does not rise even at
higher Te than Tem due to high
discharge temperature and high
pressure.
At high discharge temperature:
Refer to 1102.
At high pressure: Refer to 1302.
Refer to the page of LEV troubleshooting (9.
[4] -6- ).
Refer to the page on troubleshooting of the
outdoor unit fan.
Refer to 5106.
Refer to 1302.