41
OCH708
Check code
Abnormal points and detection method
Judgment and action
U1
(1302)
High pressure (High pressure switch
63H operated)
Abnormal if high pressure switch 63H
(4.15MPa) operated during compressor
operation.
1
Short cycle of indoor unit
2
Clogged filter of indoor unit
3
Decreased airflow caused by
dirt of indoor fan
4
Dirt of indoor heat exchanger
5
Locked indoor fan motor
6
Malfunction of indoor fan motor
7
Defective operation of stop
valve (Not full open)
8
Clogged or broken pipe
9
Locked outdoor fan motor
0
Malfunction of outdoor fan motor
1
Short cycle of outdoor unit
2
Dirt of outdoor heat exchanger
3
Decreased airflow caused by
defective inspection of outside
temperature thermistor
(It detects lower temperature
than actual temperature.)
4
Disconnection or contact failure
of connector (63H) on outdoor
controller board
5
Disconnection or contact failure
of 63H connection
6
Defective outdoor controller board
7
Defective action of linear
expansion valve
8
Malfunction of fan driving circuit
1
–
6
Check indoor unit and repair defect.
7
Check if stop valve is fully open.
8
Check piping and repair defect.
9
–
2
Check outdoor unit and repair defect.
3
Check the detected temperature of outside
temperature thermistor on LED display.
(SW2 on A-Control Service Tool : Refer
to "9-10. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
4
–
6
Turn the power off and check F5 is
displayed when the power is turned again.
When F5 is displayed, refer to “Judgment
and action” for F5.
7
Check linear expansion valve.
Refer to "9-6. HOW TO CHECK THE PARTS".
8
Replace outdoor controller board.
Case
U2
(TH4: 1102)
(TH33: 1132)
High discharging temperature
High comp. surface temperature
1. Abnormal if discharge thermistor (TH4)
exceeds 115°C
or 110°C continuously for
5 minutes.
Abnormal if condenser/evaporator
temperature thermistor (TH5) exceeds 40°C
during defrosting and discharge thermistor
(TH4) exceeds 110°C.
2. Abnormal if discharge superheat
(TH4 - TH5) increases.
All the conditions are detected simul-
taneously for 10 minutes continuously
after 6 minutes past from compressor
startup (including the thermostat indica-
tion or recovery from defrosting).
• During compressor operation (in
Cooling only)
• When discharge superheat is less than
80°C in Cooling.
• When condensing temp of TH6 is
more than -40°C. (In Cooling only.)
3. Abnormal if comp. surface temperature
thermistor (TH33) exceeds 115°C or
110°C continuously for 5 minutes.
1
Overheated compressor
operation caused by shortage
of refrigerant
2
Defective operation of stop
valve
3
Defective thermistor
4
Defective outdoor controller
board
5
Defective action of linear
expansion valve
1
Check intake superheat.
Check leakage of refrigerant.
Charge additional refrigerant.
2
Check if stop valve is fully open.
34
Turn the power off and check if U3 is
displayed when the power is on again.
When U3 is displayed, refer to
“Judgement and action” for U3.
5
Check linear expansion valve.
Refer to "9-6. HOW TO CHECK THE PARTS".
<Abnormalities detected while unit is operating>
U3
(TH4: 5104)
(TH33: 5132)
Open/short circuit of discharge
thermistor (TH4) / comp. surface
thermistor (TH33)
Abnormal if open (TH4: −20°C or less,
TH33: −20°C or less) or short (217
°C
or more) is detected during compressor
operation.
(Detection is inoperative for 10 minutes of
compressor starting process.)
1
Disconnection or contact failure
of connector (TH4/TH33) on
the outdoor controller circuit
board
2
Defective thermistor
3
Defective outdoor controller
circuit board
1
Check connection of connector (TH4/TH33)
on the outdoor controller circuit board.
Check breaking of the lead wire for
thermistor (TH4/TH33). Refer to "9-9. TEST
POINT DIAGRAM".
2
Check resistance value of thermistor (TH4/
TH33) or temperature by microprocessor.
(Thermistor/TH4/TH33: Refer to"9-6. HOW
TO CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer
to "9-10. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
3
Replace outdoor controller board.
