38
OCH738
Check Code Abnormal points and detection method
Cause
Judgment and action
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
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 "10-9. TEST POINT DIAGRAM"
2
Check resistance value of thermistor
(TH3,TH6,TH7,TH8) or check temperature by
microprocessor. (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 the case of abnormalities of
TH3, TH6 and TH7. Refer to "10-8.
EMERGENCY OPERATION"
U5
(4230)
Temperature of heat
sink
Abnormal if heat sink thermistor (TH8)
detects temperature indicated below.
ZM200/250Y ······························ 86
:
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 airflow path for cooling.
4
Check if there is something which causes
temperature rise around outdoor unit.
(Upper limit of ambient temperature is 46°C.)
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.
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.
U7
(1520)
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is
continuously detected less than or equal
to 0°C 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 "10-7. HOW TO CHECK THE
COMPONENT".
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. HOW TO CHECK THE
PARTS".
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;
• 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.)
(
)
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
Thermistor <Liquid>
Thermistor <2-phase pipe>
Thermistor <Ambient>
Thermistor <Heat sink>
