Mitsubishi Electric MSC-A07WV-E1 Service Manual page 107

13-3. 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. Indication
point
0.5-second ON
MUH type
Mis-wiring
0.5-second OFF
1
1-time flash
MUH type
Serial
signal
2.5-second OFF
Indoor coil
2-time flash
thermistor
2
Room
tempera-
2.5-second OFF
ture ther-
mistor
3-time flash
Indoor fan
3
motor
2.5-second OFF
6-time flash
MUH type
4 Defrost
thermistor
7-time flash
MUH type
Out door
5
control
system
error
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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 run.
2.5-second OFF
Outdoor unit
does not run.
2.5-second OFF
Detect method
When serial signal stops for 4
to 5 seconds after 1st on of
52C relay by POWER turning
on.
When serial signal from out-
door unit stops for 4 to 5 sec-
onds.
Detect Indoor coil/room tem-
perature thermistor short or
open circuit every 8 seconds
during operation.
When rotational frequency
feedback pulse signal is not
emit during 12-second indoor
fan operation.
When the defrost thermistor
shorts or opens after the com-
pressor start-up.
When it cannot properly read
data in the nonvolatile memo-
ry of outdoor electronic control
P.C. board.
107
Check point
Check switch SW2-2.(MU type or MUH
type)
Check wiring (visual check and conductiv-
ity check).
Check indoor electronic control
P.C.board.
Check outdoor DEICER P.C. board.
Check electrical parts.
Check resistance of thermistor.
Reconnect connector.
Check indoor electronic control P.C.board.
Disconnect connector CN211 and then
check connector CN121 - to make
2
3
sure rotational frequency feedback signal
of 1.5V or over exists.
Check indoor electronic control P.C.
board.
Check indoor fan motor.
Reconnect connector.
Check outdoor DEICER P.C. board.(MUH)
Check resistance of thermistor.
Reconnect connector.
Check outdoor control P.C. board.