Troubleshooting; Cooling Only/Fixed Speed Heat Pump - Mitsubishi Electric M Series Manual

M series
C.1.8 TROUBLESHOOTING
C.1.8.1 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.
MSC-GE20VB MSC-GE25VB MSC-GE35VB
Abnormal
No.
Operation indicator lamp
point
MUH-GA/
0.5-second ON
MXZ
1 Mis-wiring/
or Serial
signal
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
5-time flash
MXZ
Outdoor
5
power
system
6-time flash
MUH/
MXZ
6
Outdoor
thermistor
7-time flash
MUH/
MXZ
7
Outdoor
control
system
10-time flash
MXZ
Outdoor
8
refrigerant
system
error
2.5-second OFF
Abnormal
No.
Operation indicator lamp
point
Right lamp flash
MXZ
Operation
1
mode
setting
2.5-second OFF
WALL-MOUNTED Cooling Only/Fixed Speed Heat Pump
Lighted
∙ Flashing of the OPERATION INDICATOR lamp (the left-hand side lamp)
Blinking
indicates possible abnormalities.
Not lighted
Symptom
Outdoor unit
does not run.
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 run.
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 run.
Lighted
∙ Flashing of OPERATION INDICATOR lamp (right-hand side lamp) indicates
abnormality.
Blinking
∙ OPERATION INDICATOR lamp (left-hand side lamp) is lighted.
Not lighted
Symptom
Outdoor unit
operates but
indoor unit
does not run.
Condition
Serial signal from outdoor unit stops for 4 to 5
seconds.
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.
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.
It cannot properly read data in the nonvolatile
memory of the outdoor P.C. board, outdoor
unit stops.
The compressor operation has been
interrupted by LEV protection continuously 5
minutes, the compressor stops operation.
Condition
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.
C-153