19
Error Code
Abnormal point and detection method
Case
Judgment and action
U5
Temperature of heatsink
Abnormal if heatsink thermistor(TH8)
detects 95
:
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.
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 the thermistor (TH8) temperature by
microcomputer.
(SW2 on A-Control Service Tool: 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 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. (PAC-SK52ST)
(Refer to 8-7.)
W
Heatsink thermistor(TH8) is in the power
module.
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 thermis-
tor (TH3, TH32, TH6,TH7,TH8).
Refer to 8-7.
2
Check resistance value of thermistor (TH3,
TH32, TH6,TH7,TH8) or check temperature
by microcomputer.
(Thermistor/TH3,TH6,TH7,TH32,TH8:
Refer to 8-5.)
(SW2 on A-Control Service Tool: Refer to
8-8.)
3
Replace outdoor controller circuit board.
1
Disconnection or contact failure
of connectors
Outdoor controller circuit board:
TH3, TH32, TH7/6
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
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 8-7 (Outdoor power
circuit board).
4
Check compressor referring to 8-5.
5
Replace outdoor power circuit board.
U7
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is
continuously detected less than or equal
to -15
:
for 3 minutes even though linear
expansion valve has minimum open pulse
after compressor 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 8-6.
4
Check the connection or contact of LEV-A and
LEV-B on outdoor controller circuit board.
5
Check linear expansion valve.
Refer to 8-6.
Thermistors
Open detection
Short detection
Symbol
Name
TH3, TH32
Thermistor <Outdoor pipe>
-40°C or below
90°C or above
TH6
Thermistor <Outdoor 2-phase pipe>
-40°C or below
90°C or above
TH7
Thermistor <Outdoor>
-40°C or below
90°C or above
TH8
Internal thermistor
-35°C or below
170°C or above
