Mitsubishi Electric PUZ-WZ50VAA Service Manual page 35

Check code Abnormal points and detection method
Open/short of outdoor unit thermistors
(TH3, TH34, TH6, TH7, TH8, TH32 and
TH35)
Abnormal if open or short is detected during
compressor operation.
Open detection of TH3, TH34 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)
U4
(Refer to "9-7. FUNCTION OF
(TH3:5105)
SWITCHES, CONNECTORS AND
(TH6:5107)
JUMPERS".)
(TH7:5106)
(TH8:5110)
(TH32:5105)
(TH34:5105)
(TH35:5105)
Symbol
TH3
TH6
TH7
TH8
TH32
TH34
TH35
Temperature of heat sink
Abnormal if TH8 detects temperature indi-
cated below.
WZ50V, WZ60V, WZ80V ·················· 78°C
TH8: Thermistor <Heat sink>
U5
(4230)
Power module
Check abnormality by driving power module
in case overcurrent is detected.
U6
(UF or UP error condition)
(4250)
Too low superheat due to low discharge
temperature
Abnormal if discharge superheat is
continuously detected less than or equal
°C
to −15 for 3 minutes even though linear
U7
expansion valve has minimum open pulse
(1502)
after compressor starts operating for 10
minutes.
OCH816
Cause
Disconnection or contact failure
of connectors
(
Outdoor controller circuit board:
TH3, TH34, TH7/6
Outdoor power circuit board:
CN3
Defective thermistor
Defective outdoor controller
circuit board
Thermistors
Name
Thermistor <Liquid>
Thermistor <Two-phase>
Thermistor <Ambient>
Thermistor <Heat sink>
Thermistor <Liquid>
Thermistor <Plate hex liquid>
Thermistor <Suction pipe>
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
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
temperature thermistor (TH4)
Defective holder of discharge
temperature 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
35
judgment and action
Check connection of connector (TH3, TH34,
TH7/6, TH32, TH35) on the outdoor controller
)
circuit board.
Check connection of connector (CN3) on the
outdoor power circuit board. Check breaking of
the lead wire for TH3, TH34, TH6, TH7, TH8,
TH32, TH35.
Refer to "9-6.TEST POINT DIAGRAM".
Check resistance value of TH3, TH34, TH6,
TH7, TH8, TH32, TH35 or check temperature
by microprocessor. (TH3,TH34,TH6,TH7,TH8,
TH32, TH35:
Refer to "9-6.TEST POINT DIAGRAM".)
(SW2 on A-Control Service Tool:
Refer to "9-7. FUNCTION OF SWITCHES,
CONNECTORS AND JUMPERS".)
Replace outdoor controller circuit board.
Note: Emergency operation is available in
case of abnormalities of TH3, TH34,
TH6 and TH7.
Open detection
−40 °C or below
−40 °C or below
−40 °C or below
−35 °C or below
−40 °C or below
−40 °C or below
−40 °C or below
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
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 TH8 or temperature
by microprocessor.
"9-4. HOW TO CHECK THE PARTS".)
(SW2 on A-Control Service Tool: Refer to "9-7.
FUNCTION OF SWITCHES, CONNECTORS
AND JUMPERS".)
Replace outdoor power circuit board.
Replace outdoor controller circuit board.
Check facility of power supply.
Correct the wiring (U V W phase) to compressor. Refer to
• •
"9-6.TEST POINT DIAGRAM" (Outdoor power circuit board).
Check compressor referring to "9-4. HOW TO
CHECK THE PARTS".
Replace outdoor power circuit board.
Check the installation conditions of
discharge temperature thermistor (TH4).
Check the coil of linear expansion valve.
Refer to "9-5. HOW TO CHECK THE
COMPONENTS".
Check the connection or contact of LEV-A and
LEV-B on outdoor controller circuit board.
Check linear expansion valve. Refer to "9-4.
HOW TO CHECK THE PARTS".
Short detection
90 °C or above
90 °C or above
90 °C or above
102 °C or above
90 °C or above
90 °C or above
90 °C or above
°C
.)
(TH8: Refer to