Service manual

18
Error Code
Abnormal points and detection method
Case
Judgment and action
U5
Temperature of heatsink
Abnormal if heatsink thermistor (TH8)
detects temperature indicated below.
SW40/50 ··········································· 84:
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 resistance value of thermistor (TH8)
or temperature by microcomputer.
(Thermistor/TH8: Refer to 10-6.)
(SW2 on A-Control Service Tool: Refer to 10-10.)
6 Replace outdoor power circuit board.
7 Replace outdoor controller circuit board.
U4
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.
* Check which unit has abnormality in its
thermistor by switching the mode of SW2.
(PAC-SK52ST)
(Refer to 10-10.)
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.
2 Check resistance value of thermistor
(TH3,TH6,TH7,TH8) or check temperature by
microcomputer.
(Thermistor/TH3,TH6,TH7,TH8: Refer to 10-6.)
(SW2 on A-Control Service Tool: Refer to
10-10.)
3 Replace outdoor controller circuit board.
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
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 (Outdoor power
circuit board).
4 Check compressor referring to 10-6.
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 10-8.
4 Check the connection or contact of LEV-A and
LEV-B on outdoor controller circuit board.
5 Check linear expansion valve.
Refer to 10-6.
Thermistors
Open detection Short detection
Symbol Name
TH3 Thermistor <Liquid> - 40 °C or below 90 °C or above
TH6 Thermistor <2-phase pipe> - 40 °C or below 90 °C or above
TH7 Thermistor <Amibient> - 40 °C or below 90 °C or above
TH8 Thermistor <Heatsink> - 27 °C or below 102 °C or above
U8
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;
• 100 rpm or below detected continuously
for 15 seconds at 20: or more outside
air temperature.
• 50 rpm or below or 1500 rpm or more
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 action 1 above.)
OCH525