Mitsubishi Electric MS-A18WV Service Manual page 21

1. Troubleshooting check table
• The following indication applies regardless of shape of the indicator.
flashing
Operation Indicator
Before taking measures, make sure that the symptom reappears, for accurate troubleshooting.
Self check table
Abnormal
No. Operation indicator lamp
point
0.5-second ON
MS-A30WV
1
Mis-Wiring
0.5-second OFF
Indoor coil
2-time flash
thermistor
2
Room
temperature
2.5-second OFF
thermistor
3-time flash
Indoor fan
3
motor
2.5-second OFF
4-time flash
Indoor
control
4
system
2.5-second OFF
6-time flash
MU-A30WV
Outdoor
5
thermistor
7-time flash
MU-A30WV
Outdoor
6
control
system
MU-A30WV
10-time flash
Low
discharge
tempera-
7
ture
protection
2.5-second OFF
NOTE : When the indoor unit has started operation and the above 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 the
OPERATION INDICATOR lamp flashing.
· Flashing of the OPERATION INDICATOR lamp (on the left-hand side) indicates possible
abnormalities.
· The OPERATION INDICATOR lamp (on the left-hand side) is lighted during normal operation.
Symptom
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
Indoor fan repeats
12 seconds ON
and 3minutes OFF.
When the indoor
fan breaks, the
fan keeps stopping.
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
2.5-second OFF
Outdoor unit
does not
operate.
2.5-second OFF
Outdoor unit
does not
operate.
Detection method
3 minutes after power supply turns ON, when
serial signal is not received.
Detect Indoor coil/room temperature
thermistor short or open circuit every 8
seconds during operation.
When rotational frequency feedback signal is
not emitting during 12-second indoor fan
operation.
When it cannot properly read data in the
nonvolatile memory of the indoor electronic
control P.C. board.
<Thermistor short>
Thermistors are abnormal when they short
after compressor start-up.
<Thermistor open>
Thermistors are abnormal when they open
after compressor start-up.
However, discharge temperature thermistor is
abnormal when open circuit is detected more
than 10 minutes after compressor start-up.
When it cannot properly read data in the
nonvolatile memory of the deicer P.C. board,
outdoor unit stops.
When discharge temperature has been 50:
or less on cool operation.
21
Checkpoint
• Refer to D "How to check
mis-wiring " on page 25.
• Refer to the characteristics of
main indoor coil thermistor,
sub indoor coil thermistor,
and room temperature
thermistor on page 26.
• Refer to A "Check of
indoor fan motor" on page 23.
• Check the indoor electronic
control P.C. board.
• Check the deicer P.C.
board.
• Reconnect the connector.
Refer to "Check of outdoor
thermistor". Refer to service
manual OB326.
• Check the deicer P.C. board.
Refer to service manual
OB326.
• Refer to "Check of LEV".
• Check refrigerant circuit and
refrigerant amount.
Refer to service manual
OB326.