29
OCH754A
Abnormal point and detection method
Cause
Judgment and action
U5
(4230)
Temperature of heatsink
Abnormal if heat sink thermistor(TH8) detects
temperature indicated below.
KA24 ·······························
170˚F [
77°C]
KA30/36 ···························
177˚F [
81°C]
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 out-
door power circuit board
7
Failure of outdoor fan drive circuit
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 114˚F
[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 thermistor (TH8)
or temperature by microprocessor.
(Thermistor/TH8: Refer to "10-5. HOW TO
CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer
to "10-9. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS")
6
Replace outdoor power circuit board.
7
Replace outdoor controller circuit board.
U6
(4250)
Power module
Check abnormality by driving power mod-
ule in case overcurrent is detected.
(UF or UP error condition)
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
Open stop valve.
2
Check facility of power supply.
3
Correct the wiring (U·V·W phase) to com-
pressor. Refer to "10-8. TEST POINT
DIAGRAM" (Outdoor power circuit board).
4
Check compressor referring to "10-5. HOW
TO CHECK THE PARTS".
5
Replace outdoor power circuit board.
Check Code
U3
(5104)
Open/short circuit of outdoor unit
temperature thermistor (TH4, TH33)
Abnormal if open (37˚F [3
°C] or less) or
short (422˚F [217
°C] or more) is detected
during compressor operation.
(Detection is inoperative for 10 minutes
of compressor starting process and for 10
minutes after and during defrosting.)
TH4: Thermistor <Discharge>
TH33: Thermistor <Comp. surface>
1
Disconnection or contact failure
of connectors (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 break-
ing of the lead wire for TH4, TH33. Refer to "10-8.
TEST POINT DIAGRAM".
2
Check resistance value of TH4, TH33 or
temperature by microprocessor.
(Thermistor/TH4, TH33: Refer to "10-5. HOW TO
CHECK THE PARTS".) (SW2 on A-Control Service
Tool: Refer to "10-9. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
3
Replace outdoor controller board.
U4
(TH3: 5105)
(TH6: 5107)
(TH7: 5106)
(TH8: 5110)
(TH32: 5105)
1
Check connection of connector (TH3, TH32,
TH7/6) on the outdoor controller circuit board.
Check connection of connector (CN6) on the
outdoor power circuit board.
Check breaking of the lead wire for TH3,
TH32, TH6, TH7, TH8.
Refer to "10-8. TEST POINT DIAGRAM".
2
Check resistance value of TH3, TH32,
TH6, TH7, TH8 or check temperature by
microprocessor.
(TH3,TH6,TH7,TH8: Refer to "10-5. HOW TO
CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer to "10-9.
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. Refer to "10-7.
EMERGENCY OPERATION".
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
Open detection
Short detection
Symbol
Name
TH3, TH32
Thermistor <Liquid>, <Suction>
−54˚F [−
48°C] or below
194˚F [
90°C] or above
TH6
Thermistor <2-phase pipe>
−54˚F [−
48°C] or below
194˚F [
90°C] or above
TH7
Thermistor <Ambient>
−54˚F [−
48°C] or below
194˚F [
90°C] or above
TH8
Thermistor <Heatsink>
−54˚F [−
48°C] or below
216˚F [
102°C] or above
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
of SW2. (PAC-SK52ST)
(Refer to "10-9. FUNCTION OF
SWITCHES, CONNECTORS AND
JUMPERS".)
