Mitsubishi MSH-A18WV Service Manual page 22

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
Mis-Wiring
1
0.5-second OFF
Indoor coil
2-time flash
thermistor
Room
2
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
5-time flash
Outdoor
5
power
system
6-time flash
Outdoor
6
thermistor
7-time flash
Outdoor
7
control
system
MUH-A30WV
10-time flash
Low
discharge
temperature
protection
8
MXZ type
2.5-second OFF
Outdoor
refrigerant
system
error
Operation Indicator
MXZ type
Operation
9
mode
Lighted
setting
Flashing
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 lighting 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.
2.5-second OFF
Outdoor unit
does not
operate.
Outdoor unit
operates but
indoor unit
2.5-second OFF
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.
When the compressor operation is
continuously three times interrupted by over
current protection within 1 minute after start-up ,
it stops operation.
<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.
MUH type
When it cannot properly read data in the
nonvolatile memory of the deicer P.C. board,
outdoor unit stops [and restarts 3 minutes
later(MUH-24WV).]
MXZ type
When it cannot properly read data in the
nonvolatile memory of the outdoor electronic
control P.C.board.
MUH-A30WV
When discharge temperature has been 50:
or less on cool operation, or has been 49: or
less on heat operation for 20 minutes.
MXZ type
When the compressor operation has been
interrupted by LEV protection continuously 5
minutes, the compressor stops operation.
When the operation mode of each indoor unit
is differently set to COOL(includes DRY) and
HEAT at same time, the operation mode of
indoor unit that has operated at first has the
priority.
22
Checkpoint
• Refer to D "How to check
mis-wiring " on page 26.
• Refer to the characteristics of
main indoor coil thermistor,
sub indoor coil thermistor,
and room temperature
thermistor on page 27.
• Refer to A "Check of
indoor fan motor" on page 24.
• Check the indoor electronic
control P.C. board.
• Check the inverter output.
Check the compressor.
• Shortage of refrigerant
• Check the deicer P.C.
board.
Refer to "Check of outdoor
thermistor". Refer to service
manual OB322.
MUH type
• Check the deicer P.C. board.
Refer to service manual
OB322.
MXZ type
• Check the outdoor electronic
control P.C. board.
Refer to service manual
OB319.
MUH-A30WV
• Refer to "Check of LEV".
• Check refrigerant circuit and
refrigerant amount.
Refer to service manual
OB322.
MXZ type
• Refer to "Check of LEV".
• Check refrigerant circuit and
refrigerant amount.
• Check outdoor electronic
control P.C. board.
Refer to service manual
OB319.
• Unify the operation mode.