Si33-105 Troubleshooting
Troubleshooting R407C PLUS Series Heat Recovery System 181
3.25 Low Pressure Drop Due to Refrigerant Shortage or
Electronic Expansion Valve Failure
Remote
Controller
Display
U0
Supposed
Causes
!
Out of gas 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 (R6T) and
coil thermistor (R2T)
disconnected from
the outdoor unit
PC board.
Out of gas or refrigerant
system is clogged. Requires
check of refrigerant system.
Replace the thermistor.
Replace the outdoor unit PC
board (A1P).
YES
NO
NO
Out of gas 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.
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