Uo" Low Pressure Drop Due To Refrigerant Shortage Or; Electronic Expansion Valve Failure - Daikin VRV II REYQ8MY1B Service Manual

Si39-306
2.42 " UO "
Low Pressure Drop due to Refrigerant Shortage or

Electronic Expansion Valve Failure

U0
Remote
Controller
Display
Applicable REYQ8~48M
Models
Method of Short of gas malfunction is detected by discharge pipe temperature thermistor.
Malfunction
Detection
Malfunction Microcomputer judge and detect if the system is short of refrigerant.
Decision
Conditions
Supposed
Causes
Troubleshooting
∗1: Refer to thermistor resistance / temperature characteristics table on P.275.
∗2: Refer to pressure sensor, pressure / voltage characteristics table on P.277.
Troubleshooting
Malfunction is not decided while the unit operation is continued.
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
Be sure to turn off power switch before connect or disconnect connector,
Caution
or parts damage may be occurred.
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
(R2T) and coil thermistor
(R4T) disconnected
from the outdoor
unit PC
board.
∗1
YES
Troubleshooting by Indication on the Remote Controller
Low pressure
YES
is 0.1 MPa
or less.
NO
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
YES
NO
YES
Out of gas, closing of stop
valve or refrigerant system is
clogged. Requires check of
refrigerant system.
YES
Replace main outdoor unit
PC board (A1P).
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).
(V2819)
195