Daikin VRV II REYQ10MY1B, Service Manual

Page: 206 / 309

Si39-306 Troubleshooting by Indication on the Remote Controller
Troubleshooting 195
2.42
“
UO
”
Low Pressure Drop due to Refrigerant Shortage or
Electronic Expansion Valve Failure
Remote
Controller
Display
U0
Applicable
Models REYQ8~48M
Method of
Malfunction
Detection Short of gas malfunction is detected by discharge pipe temperature thermistor.
Malfunction
Decision
Conditions Microcomputer judge and detect if the system is short of refrigerant.
Malfunction is not decided while the unit operation is continued.
Supposed
Causes
„
Out of gas or refrigerant system clogging (incorrect piping)
„
Defect of pressure sensor
„
Defect of outdoor unit PC board (A1P)
„
Defect of thermistor R2T or R4T
Troubleshooting
∗
1: Refer to thermistor resistance / temperature characteristics table on P.275.
∗
2: Refer to pressure sensor, pressure / voltage characteristics table on P.277.
(V2819)
The suction
pipe temperature minus
coil temperature is 20 ˚C
or higher.
Resistance
is normal when
measured with the
suction pipe thermistor
(R2T) and coil thermistor
(R4T) disconnected
from the outdoor
unit PC
board.
∗
1
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, closing of stop
valve or refrigerant system is
clogged. Requires check of
refrigerant system.
Replace main outdoor unit
PC board (A1P).
YES
YES
NO
Cooling
Low pressure
is 0.1 MPa
or less.
The
voltage
of X45A pins (2)
and (3) on main
outdoor unit PC board
(A1P) is 0.8 VDC or less.
(Low pressure
sensor output
voltage)
∗
2
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.