Mitsubishi Electric MSZ-HM09NA-U1 Service Manual page 20

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
Upper lamp ashes.
0.5-second ON
Miswiring
1 or serial
signal
0.5-second OFF
Upper lamp ashes.
Indoor coil
2-time ash
thermistor
2
Room tem-
perature 2.5-second OFF
thermistor
Upper lamp ashes.
3-time ash
Indoor fan
3
motor
2.5-second OFF
Upper lamp ashes.
4-time ash
Indoor con-
4
trol system
Upper lamp ashes.
5-time ash
Outdoor
5 power sys-
tem
Upper lamp ashes.
6-time ash
Outdoor
6
thermistors
Upper lamp ashes.
7-time ash
Outdoor
7 control sys-
tem
Upper lamp ashes.
14-time ash or more
Other ab-
8
normality
2.5-second OFF
Outdoor
9 control sys- Upper lamp lights up.
tem
OBH746B
Lighted
Blinking
Not lighted
Symptom
2.5-second OFF
Indoor unit and
outdoor unit do
not operate.
2.5-second OFF
2.5-second OFF
2.5-second OFF
Outdoor unit
does not oper-
ate
Condition
The serial signal from the outdoor unit is not
received for 6 minutes.
The indoor coil or the room temperature ther-
mistor 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 com-
pressor 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 nonvolatile
memory of the inverter P.C. board or the out-
door electronic control P.C. board.
An abnormality other than above mentioned
is detected.
It cannot properly read data in the nonvolatile
memory of the inverter P.C. board or the out-
door electronic control P.C. board.
20
Remedy
• Refer to 9-6. "How to check
miswiring and serial signal er-
ror".
• Refer to the characteristics of
indoor coil thermistor, and the
room temperature thermistor
(9-7.).
• Refer to 9-6. "Check of in-
door fan motor".
• Replace the indoor electronic
control P.C. board.
• Refer to "How to check of in-
verter/compressor".
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.
• Check the stop valve.
• Check the 4-way valve.
• Check the abnormality in detail
using the failure mode recall
function for outdoor unit.
• Check the blinking pattern of
the LED on the inverter P.C.
board or the outdoor electronic
control P.C. board.