Mitsubishi Electric MUZ-JP WA Series Service Manual page 19

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 blinks.
OPERATION INDICATOR
Abnormal
No.
point
Upper lamp blinks.
0.5-second ON
Miswiring
1 or serial
signal
0.5-second OFF
Upper lamp blinks.
Indoor coil
2-time blink
thermistor
2
Room tem-
perature 2.5-second OFF
thermistor
Upper lamp blinks.
3-time blink
Indoor fan
3
motor
Upper lamp blinks.
4-time blink
Indoor con-
4
trol system
Upper lamp blinks.
5-time blink
Outdoor
5 power sys-
tem
Upper lamp blinks.
6-time blink
Outdoor
6
thermistors
Upper lamp blinks.
7-time blink
Outdoor
7 control sys-
tem
Upper lamp blinks.
14-time blink or more
Other ab-
8
normality
Outdoor
9 control sys- Upper lamp lights up.
tem
OBH820
Lit
Blinking
Not lit
Operation indicator lamp
2.5-second OFF
2.5-second OFF
2.5-second OFF
2.5-second OFF
2.5-second OFF
2.5-second OFF
Symptom
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.
Indoor unit and
outdoor unit do
not operate.
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.
Outdoor unit It cannot properly read data in the nonvolatile
does not oper- memory of the inverter P.C. board or the out-
ate door electronic control P.C. board.
19
Condition
• Refer to 9-6.
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.
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.
Remedy
"How to check
"Check of in-