112
Thermistors
Open detection
Short detection
Symbol
Name
TH3
TH6
TH7
TH8
– 40
:
or below
– 40
:
or below
– 40
:
or below
– 27
:
or below
90
:
or above
90
:
or above
90
:
or above
102
:
or above
Pipe temperature thermistor / Liquid
Condenser/evaporator temperature thermistor
Outside temperature thermistor
Heat sink temperature thermistor
Error Code Meaning of error code and detection method
Case
Judgment and action
U5
(4230)
Abnormal temperature of heat sink
Abnormal if heat sink thermistor(TH8)
detects temperature indicated below.
RP1.6, 2VHA·······85
:
RP2.5, 3VHA·······77
:
RP4-6VHA·····85
:
1
The outdoor fan motor is
locked.
2
Failure of outdoor fan motor
3
Air flow 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.
Refer to “(9) Operation failure of the
outdoor fan ” on page 97.
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 microcomputer.
(Thermistor/TH8: Refer to page 28.)
(SW2 on A-Control Service Tool : Refer to
page 68.)
6
Replace outdoor power circuit board.
7
Replace outdoor controller circuit board.
U6
(4250)
Abnormality of 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 page 125 and 126.
4
Check compressor referring to page 28.
5
Replace outdoor power circuit board.
U7
(1520)
Abnormality of super heat due to low
discharge temperature (RP1.6-3VHA)
Abnormal if discharge super heat is
continuously detected less than or equal
to 0
:
for 3 minutes even though linear
expansion valve has minimum open pulse
after compressor starts operating for 10
minutes.
(RP1.6-3VHA only)
1
Disconnection or loose
connection 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
connection of linear expansion
valve’s connector.
5
Defective linear expansion
valve.
12
Check the installation conditions of
discharge temperature thermistor (TH4).
3
Check the coil of linear expansion valve.
Refer to page 32.
4
Check the connection or contact of LEV-A
and LEV-B on outdoor controller circuit
board.
5
Check linear expansion valve.
Refer to page 28.
U3
(5104)
Open/short circuit of discharge
temperature thermistor (TH4)
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 (TH4) on
the outdoor controller circuit
board.
2
Defective thermistor
3
Defective outdoor controller
circuit board
1
Check connection of connector (TH4) on the
outdoor controller circuit board.
Check breaking of the lead wire for
thermistor (TH4). Refer to page 121.
2
Check resistance value of thermistor (TH4) or
temperature by microcomputer.
(Thermistor/TH4: Refer to page 28.)
(SW2 on A-Control Service Tool : Refer to
page 68.)
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.
W
Check which unit has abnormality in its
thermistor by switching the mode of
SW2.
(Refer to page 64.)
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
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 page 121,125 and 126.
2
Check resistance value of thermistor
(TH3,TH6,TH7,TH8) or check temperature by
microcomputer.
(Thermistor/TH3,TH6,TH7,TH8: Refer to page 28.)
(SW2 on A-Control Service Tool : Refer to
page 68.)
3
Replace outdoor controller circuit board.
W
Emergency operation is available in case of
abnormalities of TH3, TH6 and TH7.
Refer to page 90.
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