Troubleshooting Check Table - Mitsubishi Electric MSC-GE20VB Service Manual

10-3. TROUBLESHOOTING CHECK TABLE

• Before taking measures, make sure that the symptom reappears for accurate troubleshooting.
When the indoor unit has started operation and the following detection method has detected an abnormality
(the first detection after the power ON), the indoor electronic control P.C. board turns OFF the indoor fan motor
with the OPERATION INDICATOR lamp flashing.
Abnormal
No.
Operation indicator lamp
point
MUH-GA/
0.5-second ON
MXZ
Mis-wiring/
or Serial
signal
0.5-second OFF
1
0.5-second ON
MUH-GE
Mis-Wiring
0.5-second OFF
Indoor coil
2-time flash
thermistor
2
Room
temperature
2.5-second OFF
thermistor
3-time flash
Indoor fan
3
motor
2.5-second OFF
4-time flash
Indoor
4
control
system
2.5-second OFF
5-time flash
MXZ
Outdoor
5
power
system
6-time flash
MUH/
MXZ
6
Outdoor
thermistor
7-time flash
MUH/
MXZ
7
Outdoor
control
system
10-time flash
MXZ
Outdoor
8
refrigerant
system
error
2.5-second OFF
Operation Indicator
MXZ
Operation
9
mode
Lighted
setting
Flashing
OBH529A
· Flashing of the OPERATION INDICATOR lamp (the left-hand side lamp)
Lighted
Not lighted
Symptom
Outdoor unit
does not run.
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
Indoor fan repeats
12 seconds ON
and 3minutes OFF.
When the indoor
fan breaks, the fan
keeps stopping.
Outdoor unit
does not
operate.
Outdoor unit
does not run.
2.5-second OFF
Outdoor unit
does not
2.5-second OFF operate.
Outdoor unit
does not
operate.
2.5-second OFF
Outdoor unit
does not run.
Outdoor unit
operates but
indoor unit
2.5-second OFF
does not run.
indicates possible abnormalities.
Condition
Serial signal from outdoor unit stops for 4 to 5
seconds.
3 minutes after power supply turns ON,
serial signal is not received.
Indoor coil/room temperature thermistor
detects short or open circuit every 8 seconds
during operation.
The rotational frequency feedback signal is
not emitted for 12 seconds after indoor fan
motor is operated.
It cannot properly read data in the nonvolatile
memory of the indoor electronic control P.C.
board.
The compressor operation is
continuously three times interrupted by over
current protection within 1 minute after
start-up , it stops operation.
<Thermistor short>
Thermistors are abnormal when they short
after compressor start-up.
<Thermistor open>
Thermistors are abnormal when they open
after compressor start-up.
However, discharge temperature thermistor is
abnormal when open circuit is detected more
than 10 minutes after compressor start-up.
It cannot properly read data in the nonvolatile
memory of the outdoor P.C. board.
The compressor operation has been
interrupted by LEV protection continuously 5
minutes, the compressor stops operation.
The operation mode of each indoor unit
is differently set to COOL(includes DRY) and
HEAT at same time, the operation mode of
indoor unit that has operated at first has the
priority.
24
Remedy
• Check switch SW2- .(MU &
MUX type or MUH & MXZ
type)
• Check wiring (visual check
and conductivity check).
• Check indoor electronic
control P.C.board.
• Check outdoor DEICER P.C.
board and others.
• Check electrical parts.
• Refer to 10-5. "How to
E
check mis-wiring ".
• Refer to the characteristics
of indoor coil thermistor, and
room temperature thermistor
on 10-6.
• Refer to 10-5. "Check of
indoor fan motor".
• Check the indoor electronic
control P.C. board.
• Check the inverter output.
• Check the compressor.
• Shortage of refrigerant
• Check the deicer P.C. board
and others.
Refer to "Check of outdoor
thermistor". Refer to outdoor
service manual.
• Check the deicer P.C. board
and others.
Refer to outdoor service
manual.
• Refer to "Check of LEV".
• Check refrigerant circuit and
refrigerant amount.
• Check outdoor electronic
control P.C. board.
Refer to outdoor unit service
manual.
• Unify the operation mode.