Mitsubishi Electric MS-A09WA Service Manual page 14

8-4. 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
OPERATION INDICATOR lamp flashing.
OPERATION INDICATOR
Abnormal
No. Operation indicator lamp
point
Indoor coil
Left lamp flashes.
thermistor
2-time flash
1
Room
tempera-
2.5-second OFF
ture
thermistor
Left lamp flashes.
3-time flash
Indoor fan
2
motor
2.5-second OFF
Left lamp flashes.
Indoor
4-time flash
control
3
system
2.5-second OFF
· Flashing of OPERATION INDICATOR lamp (left-hand side lamp)
Lighted
indicates abnormalities.
Blinking
Not lighted
Symptom
Indoor unit
and outdoor
unit do not
operate.
Indoor unit
and outdoor
unit do not
operate.
Indoor unit
and outdoor
unit do not
operate.
Detection method
The indoor coil or the room temperature
thermistor is short or open circuit.
The rotational frequency feedback signal is
not emitted during the indoor fan operation.
It cannot properly read data in the nonvolatile
memory of the indoor electronic control P.C.
board.
14
Correspondence
• Refer to 8-7.the
characteristics of indoor coil
thermistor, and the room
temperature thermistor.
• Refer to 8-6.A "Check of
indoor fan motor".
• Replace the indoor electronic
control P.C. board.