38
Thermistors
Open detection
Short detection
Symbol
Name
TH3
TH6
TH7
TH8
−
40
:
or below
−
40
:
or below
−
40
:
or below
−
27
:
or below
−
35
:
or below
90
:
or above
90
:
or above
90
:
or above
102
:
or above
170
:
or above
Thermistor <Liquid>
Thermistor <2-phase pipe>
Thermistor <Ambient>
Thermistor <Heat sink> (100YHA)
TH8 Internal thermistor (VHA, 125/140YHA)
Abnormal points and detection method
Case
Judgment and action
U5
(4230)
Temperature of heatsink
Abnormal if heatsink thermistor(TH8)
detects temperature indicated below.
SP100-140V·············79
:
SP100-140Y·············85
:
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
12
Check outdoor fan.
3
Check air flow path for cooling.
4
Check if there is something which causes
temperature rise around outdoor unit.
(Upper limit of ambient temperature is 46
:
.)
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 "10-6. HOW TO CHECK
THE PARTS".) (SW2 on A-Control Service Tool:
Refer to
"10-10. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
6
Replace outdoor power circuit board.
7
Replace outdoor controller circuit board.
U3
(5104)
Open/short circuit of discharge
temperature thermistor (TH32)
Abnormal if open (3
:
or less) or short
(217
:
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.)
1
Disconnection or contact failure
of connector (TH32) on the
outdoor controller circuit board
2
Defective thermistor
3
Defective outdoor controller circuit
board
1
Check connection of connector (TH32) on
the outdoor controller circuit board. Check
breaking of the lead wire for thermistor (TH32).
Refer to "10-9. TEST POINT DIAGRAM".
2
Check resistance value of thermistor (TH32) or
temperature by microcomputer. (Thermistor TH32:
Refer to "10-6. HOW TO CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer
to "10-10. FUNC-TION OF SWITCHES,
CONNECTORS AND JUMPERS".)
3
Replace outdoor controller board.
U4
(TH3:5105)
(TH6:5107)
(TH7:5106)
(TH8:5110)
Open/short of outdoor unit thermistors
(TH3, TH6, TH7, and TH8)
Abnormal if open or short is detected
during compressor operation.
Open detection of thermistors TH3 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
"10-10. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
1
Check connection of connector (TH3,TH6/TH7) on
the outdoor controller circuit board.
Check connection of connector (CN3) on the
outdoor power circuit board. Check breaking of
the lead wire for thermistor (TH3,TH6,TH7,TH8).
Refer to "10-9. TEST POINT DIAGRAM".
2
Check resistance value of thermistor
(TH3,TH6,TH7,TH8) or check temperature by
microcomputer. (Thermistor/TH3,TH6,TH7,TH8:
Refer to "10-6. HOW TO CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer to "10-10.
FUNCTION OF SWITCHES, CONNECTORS AND
JUMPERS".)
3
Replace outdoor controller circuit board.
Note:
Emergency operation is available in case of
abnormalities of TH3, TH6 and TH7. Refer to
"10-8. EMERGENCY OPERATION".
1
Disconnection or contact failure
of connectors
Outdoor controller circuit board:
TH3,TH6/TH7
Outdoor power circuit board:
CN3
2
Defective thermistor
3
Defective outdoor controller
circuit board
U6
(4250)
Power module
Check abnormality by driving power module
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
compressor. Refer to "10-9. TEST POINT
DIAGRAM
(Outdoor power circuit board)".
4
Check compressor referring to "10-6. HOW
TO CHECK THE PARTS".
5
Replace outdoor power circuit board.
U8
(4400)
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;
• Less than 100 rpm detected continuously
for 15 seconds at 20
:
or more outside
air temperature
• Less than 50 rpm or more than 1500 rpm
detected continuously for 1 minute.
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
controller 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
OCH566A
