Mitsubishi Electric M Series Manual page 156

WALL-MOUNTED Cooling Only/Fixed Speed Heat Pump
Troubleshooting check table
• Before taking measures, make sure that the symptom reappears for accurate troubleshooting.
When the indoor unit has started operation and the following 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.
MS-GE50VB MSH-GE50VB
MS-GA60VB MSH-GA60VB
MS-GD80VB MSH-GD80VB
Abnormal
No.
Operation indicator lamp
point
0.5-second ON
MU-GD80
1 MUH
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
4
control
system
2.5-second OFF
MU-GD80
6-time flash
MUH
Outdoor
5
thermistor
7-time flash
MU-GD80
MUH
6 Outdoor
control
system
10-time flash
MU-GD80
MUH-GD80
Low
7
discharge
temperature
protection
2.5-second OFF
C-154
∙ Flashing of the OPERATION INDICATOR lamp (the left-hand side lamp)
Lighted
indicates possible abnormalities.
Blinking
Not lighted
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
2.5-second OFF operate.
Outdoor unit
does not
operate.
2.5-second OFF
Outdoor unit
does not
operate.
Condition
3 minutes after power supply turns ON,
serial signal is not received.
Indoor coil/room temperature thermistor
detects short or open circuit every 8 seconds
during operation.
The rotational frequency feedback signal is
not emitted for 12 seconds after indoor fan
motor is operated.
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.
It cannot properly read data in the nonvolatile
memory of the deicer P.C. board, outdoor unit
stops [and restarts 3 minuites later
(MUH-GA60)].
Discharge temperature has been 50
or less on cool operation, [or has been 49
or less on heat operation for 20 minutes
(MUH-GD80)].
M series