Mitsubishi Electric PUZ-SM100VKA2 Service Manual page 32

Abnormal points and detection method
Check code
Open/short of outdoor unit thermistors
(TH3, TH6, TH7, and TH8)
Abnormal if open or short is detected
during compressor operation.
Open detection of thermistor TH3 and TH6
is inoperative for 10 seconds to 10 minutes
after compressor started.
Note:
Check which unit has abnormality in its
thermistor by switching the mode of SW2.
(PAC-SK52ST)
U4
(Refer to "9-9. FUNCTION OF SWITCHES,
(TH3: 5105)
CONNECTORS AND JUMPERS".)
(TH6: 5107)
(TH7: 5106)
(TH8: 5110)
Symbol
TH3
TH6
TH7
TH8
Temperature of heatsink
Abnormal if heatsink thermistor (TH8)
detects temperature indicated below.
PUZ-SM100VKA2 ······················ 71 °C
PUZ-SM125/140VKA2 ················ 74 °C
PUZ-SM·YKA2 ·························· 77 °C
U5
(4230)
Power module
Check abnormality by driving power module
in case overcurrent is detected.
(UF or UP error condition)
U6
(4250)
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is
continuously detected less than or equal
to −15°C for 3 minutes even though linear
U7
expansion valve has minimum open pulse
(1520)
after compressor starts operating for 10
minutes.
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;
U8
• 100 rpm or below detected continuously
(4400)
for 15 seconds at 20°C or more outside
air temperature.
• 50 rpm or below or 1500 rpm or more
detected continuously for 1 minute.
OCH774A
Cause
Disconnection or contact failure
of connectors
(
Outdoor controller circuit
board: TH3, TH6/TH7
Outdoor power circuit board:
CN6
Defective thermistor
Defective outdoor controller
circuit board
Thermistors
Name
Thermistor <Liquid>
Thermistor <2-phase pipe>
Thermistor <Ambient>
Thermistor <Heatsink>
The outdoor fan motor is
locked.
Failure of outdoor fan motor
Airflow path is clogged.
Rise of ambient temperature
Defective thermistor
Defective input circuit of
outdoor power circuit board
Failure of outdoor fan drive
circuit
Outdoor stop valve is closed.
Decrease of power supply voltage
Looseness, disconnection or
reverse of compressor wiring
connection
Defective compressor
Defective outdoor power circuit
board
Disconnection or loose
connection of Discharge
thermistor (TH4)
Defective holder of Discharge
thermistor
Disconnection or loose connection
of linear expansion valve's coil
Disconnection or loose
connection of linear expansion
valve's connector
Defective linear expansion valve
Failure in the operation of the
DC fan motor
Failure in the outdoor circuit
controller board
32
Judgment and action
Check connection of connector (TH3, TH6/TH7)
on the outdoor controller circuit board. Check
)
connection of connector (CN6) on the outdoor
power circuit board. Check breaking of the
lead wire for thermistor TH3, TH6, TH7, and
TH8). Refer to "9-8. TEST POINT DIAGRAM".
Check resistance value of thermistor (TH3,
TH6, TH7, and TH8) or check temperature by
microprocessor. (Thermistor/TH3, TH6, TH7,
and TH8: Refer to "9-5. HOW TO CHECK THE
PARTS".)
(SW2 on A-Control Service Tool: Refer to "9-9.
FUNCTION OF SWITCHES, CONNECTORS
AND JUMPERS")
Replace outdoor controller circuit board.
Note: Emergency operation is available in
case of abnormalities of TH3, TH6
and TH7. Refer to "9-7. EMERGENCY
OPERATION".
Open detection Short detection
−48 : or below 90 : or above
−48 : or below 90 : or above
−48 : or below 90 : or above
−27 : or below 102 : or above
Check outdoor fan.
Check airflow path for cooling.
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.
Check resistance value of thermistor (TH8)
or temperature by microcomputer.
(Thermistor/TH8: Refer to "9-5. HOW TO
CHECK THE PARTS".) (SW2 on A-Control
Service Tool: Refer to "9-9. FUNCTION OF
SWITCHES, CONNECTORS AND JUMPERS".)
Replace outdoor power circuit board.
Replace outdoor controller circuit board.
Open stop valve.
Check facility of power supply.
Correct the wiring (U V W phase) to
• •
compressor. Refer to "9-8. TEST POINT
DIAGRAM (Outdoor power circuit board)".
Check compressor referring to "9-5. HOW TO
CHECK THE PARTS".
Replace outdoor power circuit board.
Check the installation conditions of
discharge thermistor (TH4).
Check the coil of linear expansion valve.
Refer to "9-6.HOW TO CHECK THE COMPONENT".
Check the connection or contact of LEV-A
and LEV-B on outdoor controller circuit
board.
Check linear expansion valve.
Refer to "9-5. HOW TO CHECK THE PARTS"
Check or replace the DC fan motor.
Check the voltage of the outdoor circuit
controller board during operation.
Replace the outdoor circuit controller board.
(when the failure is still indicated even after
performing the action above.)