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Check code Abnormal point and detection method
Open/short of outdoor unit thermistors
(TH3, TH32, TH6, TH7, and TH8)
Abnormal if open or short is detected
during compressor operation.
Open detection of TH3, TH32 and TH6 is
inoperative for 10 seconds to 10 minutes
after compressor starting and 10 minutes
after and during defrosting.
Note: Check which unit has abnormality in
its thermistor by switching the mode
U4
of SW2. (PAC-SK52ST)
(TH3:5105)
(Refer to "9-7. FUNCTION OF
(TH6:5107)
SWITCHES, CONNECTORS AND
(TH7:5106)
JUMPERS".)
(TH8:5110)
(TH32:5105)
Symbol
TH3,TH32
TH6
TH7
TH8
Temperature of heat sink
Abnormal if TH8 detects temperature indi-
cated below.
SWM60, 80, 100, 120V,
SHWM60, 80, 100, 120V ················· 78°C
SHWM140V ······································ 87°C
SWM80, 100, 120Y,
SHWM80, 100, 120, 140Y ··············· 85°C
U5
(4230)
TH8: Thermistor <Heat sink>
Power module
Check abnormality by driving power mod-
ule in case overcurrent is detected.
U6
(UF or UP error condition)
(4250)
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;
U8
• 100 rpm or below detected continuously
(4400)
for 15 seconds at 20°C or more outside
air temperature.
• 50 rpm or below or 1500 rpm or more
detected continuously for 1 minute.
OCH756
Cause
1 Disconnection or contact failure
of connectors
(
Outdoor controller circuit board:
TH3, TH32, TH7/6
Outdoor power circuit board:
CN6
2 Defective thermistor
3 Defective outdoor controller
circuit board
Thermistors
Name
Thermistor <Liquid>, <Suction>
Thermistor <2-phase pipe>
Thermistor <Ambient>
Thermistor <Heat sink>
1 The outdoor fan motor is locked.
2 Failure of outdoor fan motor
3 Airflow path is clogged.
4 Rise of ambient temperature
5 Defective thermistor
6 Defective input circuit of outdoor
power circuit board
7 Failure of outdoor fan drive circuit
1 Outdoor stop valve is closed.
2 Decrease of power supply voltage
3 Looseness, disconnection or converse
of compressor wiring connection
4 Defective compressor
5 Defective outdoor power circuit board
1 Failure in the operation of the
DC fan motor
23 Failure in the outdoor circuit
controller board
25
Judgment and action
1 Check connection of connector (TH3, TH32,
TH7/6) on the outdoor controller circuit board.
)
Check connection of connector (CN3) on the
outdoor power circuit board. Check breaking of
the lead wire for TH3, TH32, TH6, TH7, TH8.
Refer to "9-6.TEST POINT DIAGRAM".
2 Check resistance value of TH3, TH32,
TH6,TH7,TH8 or check temperature by
microprocessor.
(TH3,TH6,TH7,TH8: Refer to "9-6.TEST
POINT DIAGRAM".) (SW2 on A-Control
Service Tool: Refer to "9-7. FUNCTION OF
SWITCHES, CONNECTORS AND
JUMPERS".)
3 Replace outdoor controller circuit board.
Note: Emergency operation is available in the case
of abnormalities of TH3, TH32, TH6 and
TH7.
Open detection
−40 °C or below
−40 °C or below
−40 °C or below
−35 °C or below
12 Check outdoor fan.
3 Check airflow path for cooling.
4 Check if there is something which causes
temperature rise around outdoor unit.
(Upper limit of ambient temperature is 46°C.)
Turn off power, and on again to check if U5 is
displayed within 30 minutes.
If U4 is displayed instead of U5, follow the
action to be taken for U4.
5 Check resistance value of TH8 or temperature
by microprocessor.
"9-4. HOW TO CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer to "9-7.
FUNCTION OF SWITCHES, CONNECTORS
AND JUMPERS".)
6 Replace outdoor power circuit board.
7 Replace outdoor controller circuit board.
1 Open stop valve.
2 Check facility of power supply.
3 Correct the wiring (U
V
W phase) to compressor. Refer to "9-6.
•
•
TEST POINT DIAGRAM" (Outdoor power circuit board).
4 Check compressor referring to "9-4. HOW TO
CHECK THE PARTS".
5 Replace outdoor power circuit board.
1 Check or replace the DC fan motor.
2 Check the voltage of the outdoor circuit
controller board during operation.
3 Replace the outdoor circuit controller board.
(When the failure is still indicated even after
performing the action 1 above.)
Short detection
90 °C or above
90 °C or above
90 °C or above
102 °C or above
(TH8: Refer to
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