Uo" Low Pressure Drop Due To Refrigerant Shortage Or Electronic Expansion Valve Failure - Daikin R-410A Service Manual

Troubleshooting by Indication on the Remote Controller
4.35 "UO" Low Pressure Drop Due to Refrigerant Shortage or
Electronic Expansion Valve Failure
U0
Remote
Controller
Display
Applicable
AII outdoor unit models
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.
HMalfunction is not decided while the unit operation is continued.
Decision
Conditions
! Out of gas or refrigerant system clogging (incorrect piping)
Supposed
! Defect of thermistor R2T or R4T
Causes
! Defect of pressure sensor
! Defect of outdoor unit PC board (A1P)
Troubleshooting
150
Be sure to turn off power switch before connect or disconnect connector,
Caution
or parts damage may be occurred.
YES
Cooling
NO
The suction pipe
YES
temperature minus coil
temperature is 20 °C
or higher.
NO
Resistance
is normal when
measured with the
suction pipe thermistor
NO
(R2T) and coil thermistor
(R4T) disconnected from
the outdoor unit PC
board.(3.5kΩ
to 360 kΩ)
YES
YES
Low pressure
is 0.1 MPa or
less.
NO
The
voltage
of X45A pins (2)
and (3) on main
YES
outdoor unit PC board
(A1P) is 0.8 VDC or less.
(Low pressure
sensor output
voltage)
NO
SiBE39-402A
Out of gas, closing of stop
valve or refrigerant system is
clogged.
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)
Troubleshooting