17
Thermistors
Open detection Short detection
Symbol
Name
TH3
TH6
TH7
TH8
– 40
or below
– 40
or below
– 40
or below
– 40
or below
– 35
or below
90
or above
90
or above
90
or above
102
or above
102
or above
Thermistor <Liquid temperature>
Thermistor <Inlet water temperature>
Thermistor <Plate HEX liquid temperature>
Thermistor <Ambient temperature>
Thermistor <Heatsink temperature>
TH32
Error Code
Abnormal point and detection method
Case
Judgment and action
U5
Temperature of heatsink
Abnormal if heatsink thermistor (TH8)
detects temperature indicated below.
W85V ••••••••••••••••••• 77°C
1
The outdoor fan motor is
locked.
2
Failure of outdoor fan motor
3
Air flow path is clogged.
4
Ambient temperature is high.
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, refer to
error code U4.
5
Check resistance value of thermistor (TH8)
or temperature by microcomputer.
(Thermistor/TH8: Refer to 8-5.)
(SW2: Refer to 8-7.)
6
Replace outdoor power circuit board.
7
Replace outdoor controller circuit board.
U4
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 thermistors TH3, TH32
and TH6 is not detected for 10 seconds to
10 minutes after compressor starting and
10 minutes after and during defrosting.
Check which unit has abnormality in
its thermistor by switching the mode of
SW2.
(Refer to 8-7.)
1
Check connection of connector (TH3, TH32,
TH6/TH7) on the outdoor controller circuit board.
Check connection of connector (CN3) on the
outdoor power circuit board.
Check the lead wire for thermistor (TH3,
TH32, TH6, TH7, TH8). Refer to 8-6.
2
Check resistance value of thermistor (TH3,
TH32, TH6, TH7, TH8) or check temperature
on LED display.
(Thermistor/TH3, TH32, TH6, TH7, TH8:
Refer to 8-5.)
(SW2: Refer to 8-7.)
3
Replace outdoor controller circuit board.
1
Disconnection or contact failure
of connectors
Outdoor controller circuit
board: TH3, TH32,
TH6/TH7
Outdoor power circuit board:
CN3
2
Defective thermistor
3
Defective outdoor controller
circuit
board
(
)
U6
Power module
Check abnormality by driving power module
in case overcurrent is detected.
(UF or UP error condition)
1
Defective outdoor power circuit
board
2
Decrease of power supply voltage
3
Loosens, disconnection or
reverse of compressor wiring
connection
4
Defective compressor
1
Replace outdoor power circuit board.
2
Check facility of power supply.
3
Correct the wiring (U
•
V
•
W phase) to
compressor. Refer to 8-6 (Outdoor power
circuit board).
4
Check compressor referring to 8-4.
U7
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is
continuously detected -15
:
or less for
3 minutes even though linear expansion
valve has minimum open pulse after com-
pressor starts operating for 10 minutes.
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 8-5.
4
Check the connection or contact of LEV-A and
LEV-B on outdoor controller circuit board.
5
Check linear expansion valve.
Refer to 8-4.
