30
OCH754A
U7
(1502)
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is con-
tinuously detected less than or equal to
5˚F [−15˚C] for 3 minutes even though
linear expansion valve has minimum open
pulse after compressor starts operating for
10 minutes.
1
Disconnection or loose connec-
tion of discharge temperature
thermistor (TH4)
2
Defective holder of discharge
temperature thermistor
3
Disconnection or loose connection
of linear expansion valve’s coil
4
Disconnection or loose connec-
tion of linear expansion valve’s
connector
5
Defective linear expansion valve
12
Check the installation conditions of dis-
charge temperature thermistor (TH4).
3
Check the coil of linear expansion valve.
Refer to "10-6. HOW TO CHECK THE
COMPONENTS".
4
Check the connection or contact of LEV-A and
LEV-B on outdoor controller circuit board.
5
Check linear expansion valve. Refer to "10-5.
HOW TO CHECK THE PARTS".
Abnormal point and detection method
Cause
Judgment and action
U8
(4400)
1
Failure in the operation of the
DC fan motor
2
Failure in the outdoor circuit
controller board
1
Check or replace the DC fan motor.
2
Check the voltage of the outdoor circuit con-
troller board during operation.
3
Replace the outdoor circuit controller board.
(when the failure is still indicated even after
performing the remedy
1
above.)
Check Code
Outdoor fan motor
Abnormal if rotational frequency of the fan
motor is not detected during DC fan motor
operation.
Fan motor rotational frequency is abnormal if;
• 100 rpm or below detected continuously
for 15 seconds at 68
-
F [20°C] or more
outside air temperature.
• 50 rpm or below or 1500 rpm or more
detected continuously for 1 minute.
U9
(4220)
Detailed
codes
To find out the detail history (latest) about U9 error, turn ON SW2-1, 2-2 and 2-6.
Refer to "10-9. FUNCTION OF SWITCHES, CONNECTORS AND JUMPERS".
01
Overvoltage error
• Increase in DC bus voltage to
430 V
1
Abnormal increase in power
source voltage
2
Disconnection of compressor
wiring
3
Defective outdoor power circuit
board
4
Compressor has a ground fault.
1
Check the field facility for the power supply.
2
Correct the wiring (U.V.W phase) to
compressor. Refer to "10-8. TEST POINT
DIAGRAM" (Outdoor power circuit board).
3
Replace outdoor power circuit board.
4
Check compressor for electrical insulation.
Replace compressor.
02
Undervoltage error
• Instantaneous decrease in DC
bus voltage to 200 V
1
Decrease in power source
voltage, instantaneous stop.
2
Defective converter drive circuit
in outdoor power circuit board
3
Defective 52C drive circuit in
outdoor power circuit board
4
Disconnection or loose
connection of CN2 on the
outdoor power circuit board /
controller circuit board
5
Power circuit failure on DC
supply for 15 VDC output on
outdoor controller circuit board
1
Check the field facility for the power supply.
2
Replace outdoor power circuit board.
3
Replace outdoor power circuit board.
4
Check CN2 wiring.
5
Replace outdoor controller circuit board.
04
Input current sensor error
• Decrease in input current
through outdoor unit to 0.5 A
only if operation frequency is
more than or equal to 40 Hz
or compressor current is more
than or equal to 6 A.
1
Defective input current detection
circuit in outdoor power circuit
board
2
Defective outdoor controller
circuit board
1
Replace outdoor power circuit board.
2
Replace outdoor controller circuit board.
