Troubleshooting Check Table - Mitsubishi Electric MSC-CB20VB Service Manual

9-3. Troubleshooting check table

• The following indication does not depend on the shape of lamp.
flashing
Operation Indicator
· Flashing of the OPERATION INDICATOR lamp (on the left-hand side) indicates possible abnormalities.
· The OPERATION INDICATOR lamp (on the left-hand side) is lighting during normal operation.
Before taking measures, make sure that the symptom reappears, for accurate troubleshooting.
Self check table
Abnormal
No. Operation indicator lamp
point
MUH or
0.5-second ON
MXZ type
1
Mis-wiring
or Serial
signal
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
control
4
system
2.5-second OFF
5-time flash
MXZ type
Outdoor
5
power
system
6-time flash
MUH or
MXZ type
6
Defrost
thermistor
MUH or
7-time flash
MXZ type
Outdoor
7
control
system
error
10-time flash
MXZ type
Outdoor
refrigerant
8
system
error
2.5-second OFF
Operation Indicator
MXZ type
Operation
9
mode
Lighted
setting
Flashing
Symptom
Outdoor unit
does not run.
Outdoor unit
does not run.
Indoor fan motor
repeats 12 sec-
onds ON and 3
minutes OFF.
When the indoor
fan motor
breaks, the fan
keeps stopping.
Outdoor unit
does not
operate.
Outdoor unit
does not run.
2.5-second OFF
Outdoor unit
does not run.
2.5-second OFF
Outdoor unit
does not run.
2.5-second OFF
Outdoor unit
does not run.
Outdoor unit
operates but
indoor unit
2.5-second OFF
does not run.
Detection method
When serial signal from outdoor unit stops for
4 to 5 seconds.
Detect Indoor coil/room temperature thermis-
tor short or open circuit every 8 seconds dur-
ing operation.
When rotational frequency feedback pulse
signal is not emit during 12-second indoor fan
operation.
When it cannot properly read data in the
nonvolatile memory of indoor electronic
control P.C. board.
When the compressor operation is
continuously three times interrupted by over
current protection within 1 minute after start-
up , it stops operation.
When the defrost thermistor shorts or opens
after the compressor start-up.
When it cannot properly read data in the non-
volatile memory of outdoor electronic control
P.C. board.
When the compressor operation has been in-
terrupted by LEV protection continuously 5
minutes, the compressor stops operation.
When 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.
13
Checkpoint
Check switch SW2-2.(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.
Check resistance of
thermistor.
Reconnect connector.
Check indoor electronic
control P.C.board.
Disconnect connector
CN211 and then check
connector CN121 2-3 to
make sure rotational
frequency feedback signal of
1.5V or over exists.
Check indoor electronic
control P.C. board.
Check indoor fan motor.
Reconnect connector.
Replace the indoor electronic
control P.C. board.
Check the inverter output.
Check the compressor.
Check outdoor DEICER P.C.
board and others.
Check resistance of
thermistor.
Reconnect connector.
Refer to service manual
OB387 or OB319.
Check outdoor DEICER P.C.
board and others.
Refer to service manual
OB387 or OB319.
Refer to "Check of LEV".
Check refrigerant circuit and
refrigerant amount.
Check outdoor electronic
control P.C. board.
Refer to service manual
OB319.
Unify the operation mode.