Mitsubishi Electric MS-18NN Series Service Manual page 25

10-2 Instruction of troubleshooting
Indoor unit oper-
ates. Outdoor unit
doesn't operate.
Outdoor unit
Outdoor unit
doesn't oper-
operates in
ate even in
only Test
Test Run
Run mode.
mode.
Refer to
Check room
"Check of
temperature
outdoor unit"
thermistor.
on page 28.
10-2-1 troubleshooting check table
Operation Indicator
Before taking measures make sure that the symptom reappears, for accurate troubleshooting.
Self check table
Abnormal
NO.
point
Indoor coil
2-time flash
thermistor
1
Room
tempera-
2.5-second OFF
ture ther-
mistor
3-time flash
Indoor fan
2
motor
2.5-second OFF
Indoor unit
dosen't receive
the signal from
remote
controller.
Refer to
B
"Check of
receiver P.C.
board" on page
27.
D
Indication
Outdoor unit
does not run.
Indoor fan
repeats 12 sec-
onds ON and 3
minutes OFF.
When the indoor
fan breaks, the
fan keeps stop-
ping.
Start
Indoor unit operation
monitor lamp is flashing
2-time flash
2.5-second OFF
3-time flash
2.5-second OFF
Cause:Indoor unit
2-time-Room temperature/Indoor coil thermistor trouble.
3-times-Indoor fan motor trouble
Refer to
Check indoor coil
"Check of indoor
thermistor. Refer
fan motor" on
to"Test point dia-
page 27.
gram and voltage"
on page 29.
Symptom Detect method
Detects Indoor coil/room tem-
perature thermistor short or
open circuit every 2 seconds
during operation.
When rotational frequency
feedback pulse signal is not
emit during 12-second indoor
fan operation
Indoor unit doesn't
receive the signal from
remote controller.
Also, operation monitor
lamp doesn't flash, when
the emergency operation
switch is pressed.
Refer to C "Check of
indoor electric control
P.C. board" on page 28.
Check room temperature.
A
Refer to"Test point dia-
gram and voltage" on
page 29.
Repair
Check thermistor calibration
Reconnect connector
Check indoor borad
Disconnect connector CN211 and then
check connector CN121
sure rotational frequency feedback signal
of on 1.5V or over exists.
Check indoor electronic control P.C.
board.
Check indoor fan motor
Reconnect conector
- to make
2 3
25