Low Pressure Drop Due To Refrigerant Shortage; Or Electronic Expansion Valve Failure - Daikin VRV R-407C PLUS Series Service Manual

SiE 00-07
3.25 Low Pressure Drop Due to Refrigerant Shortage or Electronic Expansion
Valve Failure
U0
Remote Controller
Display
Supposed Causes
Troubleshooting
Troubleshooting R-407C PLUS Series
Out of gas or refrigerant system clogging (incorrect piping)
Defect of pressure sensor
Defect of outdoor unit PC board
Cooling
NO
The suction
pipe temperature minus
coil temperature is 20 ˚C
or higher.
NO
Resistance
is normal when
measured with the suction
pipe thermistor (R4T) and
coil thermistor (R2T)
disconnected
from the outdoor
unit PC
board.
YES
Low pressure
YES
is 1.0 kg/cm² (0.098 MPa) or
less.
NO
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
YES
NO
Troubleshooting
YES
Out of gas or refrigerant system is
clogged. Requires check of
refrigerant system.
YES
Replace low outdoor unit PC
board.
Replace low pressure sensor.
Out of gas or refrigerant system is
clogged. Requires check of
refrigerant system.
Replace the thermistor.
Replace the outdoor unit PC
board (A1P).
(VF052)
147