Panasonic CU-8ME1XPK - Low Pressure Drop Due to Refrigerant Shortage or Electronic Expansion Valve Failure

Troubleshooting PACD011001C2
522 Troubleshooting UM Combination “MA1R Series” Using R-407C
3.25 Low Pressure Drop Due to Refrigerant Shortage or Electronic Expansion
Valve Failure
Remote Controller
Display
U0
Supposed Causes
„
Refrigerant shortage or refrigerant system clogging (incorrect piping)
„
Defect of pressure sensor
„
Defect of outdoor unit PC board
Troubleshooting
(VF052)
The suction
pipe temperature minus
coil temperature is 20 ˚C
or higher.
Resistance
is normal when
measured with the suction
pipe thermistor (R4T) and
coil thermistor (R2T)
disconnected
from the outdoor
unit PC
board.
Refrigerant shortage or refrigerant
system is clogged. Requires
check of refrigerant system.
Replace the thermistor.
Replace the outdoor unit PC
board (A1P).
YES
NO
NO
Refrigerant shortage or refrigerant
system is clogged. Requires check
of refrigerant system.
Replace low outdoor unit PC
board.
YES
YES
NO
Cooling
Low pressure
is 1.0 kg/cm² (0.098 MPa) or
less.
The voltage
of X21A pins (2)
and (3) on both sides of
outdoor unit PC board (A1P) is
0.8 VDC or less.
(Pressure sensor
output
voltage)
NO
NO
YES
YES
Replace low pressure sensor.
Caution
Be sure to turn off power switch before connect or disconnect connector,
or parts damage may be occurred.