Mitsubishi Electric MUZ-D-NA Series Service Manual page 23

9-4. TROUBLESHOOTING CHECK TABLE
Before taking measures, make sure that the symptom reappears for accurate troubleshooting.
When the indoor unit has started operation and detected an abnormality of the following condition (the first detection after the
power ON), the indoor fan motor turns OFF and OPERATION INDICATOR lamp flashes.
OPERATION INDICATOR
Abnormal
No. Operation indicator lamp
point
Left lamp fl ashes.
0.5-second ON
1 Miswiring or
serial signal
0.5-second OFF
Left lamp fl ashes.
Indoor coil
2-time fl ash
thermistor
2
Room
2.5-second OFF
temperature
thermistor
Left lamp fl ashes.
3-time fl ash
3 Indoor fan
motor
2.5-second OFF
Left lamp fl ashes.
4-time fl ash
4 Indoor con-
trol system
2.5-second OFF
Left lamp fl ashes.
5-time fl ash
Outdoor
5 power sys-
tem
Left lamp fl ashes.
6-time fl ash
6 Outdoor
thermistors
Left lamp fl ashes.
7-time fl ash
Outdoor con-
7
trol system
Left lamp fl ashes.
14-time fl ash
Other abnor-
8
mality
2.5-second OFF
Lighted
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.
Indoor unit
and outdoor
unit do not
operate.
Indoor unit
and outdoor
unit do not
operate.
2.5-second OFF
Indoor unit
and outdoor
unit do not
operate.
2.5-second OFF
Indoor unit
and outdoor
unit do not
operate.
2.5-second OFF
Indoor unit
and outdoor
unit do not
operate.
Condition
The serial signal from the outdoor unit is not
received for a maximum of 6 minutes.
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.
It consecutively occurs 3 times that the
compressor stops for overcurrent protection or
start-up failure protection within 1 minute after
start-up.
The outdoor thermistors short or open circuit
during the compressor operation.
It cannot properly read data in the nonvola-
tile memory of the inverter P.C. board or the
outdoor electronic control P.C. board.
An abnormality other than above mentioned is
detected.
23
Remedy
• Refer to 9-6. "How to check miswiring
and serial signal error".
• Refer to 9-7.the characteristics of indoor
coil thermistor, and the room tempera-
ture thermistor.
• Refer to 9-6. "Check of indoor fan mo-
tor".
• Replace the indoor electronic control
P.C. board.
• Refer to "How to check of inverter/com-
pressor".
Refer to outdoor unit service manual.
• Check the stop valve.
• Refer to "Check of outdoor thermistor".
Refer to outdoor unit service manual.
• Replace the inverter P.C. board or the
outdoor electronic control P.C. board.
Refer to outdoor unit service manual.
• Confi rm the abnormality in detail using
the failure mode recall function for
outdoor unit.