Mitsubishi Electric MSC-CB20VB, Service Manual

Page: 12 / 24

12
9-2. Instruction of troubleshooting
Start
Indoor unit
operates.
Outdoor unit
doesn't
operate.
Indoor unit
doesn't receive
the signal from
remote controller.
Indoor unit
operates.
Outdoor unit
doesn't operate
normally.
OPERATION
INDICATOR
lamp on the
indoor unit is
flashing on
and off.
Outdoor unit
operates in
only Test Run
operation. Outdoor unit
doesn't
operate
even in
Test Run
operation.
Indoor unit
operates,
when the
EMERGENCY
OPERATION
switch is
pressed.
Indoor unit
doesn't operate,
when the
EMERGENCY
OPERATION
switch is
pressed.
Check room
temperature
thermistor.
Refer to 9-6.
"Test point
diagram and
voltage".
MUH-GA20/GA25/GA35VB
MUX-2A28/2A59/3A60/
3A63/2A70/4A73VB
Refer to
"Check of
outdoor unit". Refer to 9-5.
B
"Check of
remote
controller
and receiver
P.C. board".
MUH-GA20/GA25/GA35VB
MXZ-A14/A18WV
Flash on and off at
0.5-second intervals
Cause:
Indoor/Outdoor unit
• Mis-wiring or
trouble of serial signal
2-time flash
Cause:
Indoor unit
• Trouble of
room temp-
erature/
indoor coil
thermistor
3-time flash
Cause:
Indoor unit
• Trouble of
indoor fan
motor
6-time flash
Cause:
Outdoor unit
• Trouble of
thermistor
in outdoor
unit
7-time flash
Cause:
Outdoor unit
• Trouble of
outdoor
control
system
Check room
temperature
thermistor
and indoor
coil thermis-
tor.
Refer to 9-6.
"Test point
diagram and
voltage".
Refer to 9-5.
A
"Check of
indoor fan
motor".
4-time flash
Cause:
Indoor unit
• Trouble of
indoor unit
control
system
Replace the
indoor
electronic
control
P.C. board.
MUH-GA20/GA25/GA35VB
MXZ-A14/A18WV
Refer to
"Check of
outdoor
thermistor"
and others.
MUH-GA20/GA25/GA35VB
MXZ-A14/A18WV
Replace the
deicer
P.C. board
and others.
Refer to 9-5.
D
"How to
check mis-wiring and serial
signal error (When outdoor
unit doesn't work)".
W
1
1. Check indoor /
outdoor
connecting wire.
2. Refer to 9-5.
C
"Check of indoor
electronic control
P.C. board".
Outdoor unit
doesn't
stop even
if indoor unit
stops. Unit doesn't
operate
normal
operation in
COOL or
HEAT mode.
MU-GA20/GA25/GA35VB
Check of wiring
diagram of
outdoor unit".
MUH-GA20/GA25/GA35VB
Refer to
"Check of
outdoor unit".
MUH-GA20/GA25/GA35VB
MXZ-A14/A18WV
Refer to
"Check of
R.V. coil" and
others.
W
1.<The case of the trouble of the serial signal>
When the power is turned off and then turned on again, the indication shows “the trouble of mis-wiring”.
As for outdoor unit MU type, refer to service manual OB386.
As for outdoor unit MUH type, refer to service manual OB387.
As for outdoor unit MUX type, refer to service manual OB384.
As for outdoor unit MXZ type, refer to service manual OB319.
Indoor unit
operates.
But indoor
unit doesn't
blow out
cool air.
MUX-2A28/2A59/3A60/
3A63/2A70/4A73VB
Refer to
"Check of
indoor/outdoor
units' connection
and outdoor
unit".
10-time flash
Cause:
Outdoor unit
MXZ type
• Outdoor
refrigerant
system
abnormality
MXZ type
Refer to
outdoor
refrigerant
system
related items.
MXZ type
5-time flash
Cause:
Outdoor unit
• Outdoor
power
system
abnormality
Refer to
"Check of
inverter/
compressor"
and "Check
of power
supply".
MSC-CB20VB
MSC-CB25VB
MSC-CB35VB
OB439-1.qxp 05.12.6 9:10 AM Page 12