Troubleshooting Check Table - Mitsubishi Electric MSH09TW Service Manual

1. Troubleshooting check table

MSH09TW
MSH09TW -
U1
MSH12TN
MSH12TN -
U1
MSH15TN MSH15TN -
U1
MSH17TN -
MSH17TN
U1
• The following indication applies regardless of shape of the indicatior.
flashing
Operation Indicator
Before taking measures, make sure that the symptom reappears, for accurate troubleshooting.
Self check table
Abnormal
NO.
point
0.5-second ON
Mis-wiring
0.5-second OFF
1
1-time flash
Serial sig-
nal
2.5-second OFF
Indoor coil
2-time flash
thermistor
2
Room
tempera-
2.5-second OFF
ture ther-
mistor
<MSH09>
3-time flash
Indoor fan
3
motor
2.5-second OFF
6-time flash
Outdoor
4
thermistor
MUH09TW
MUH09TW -
MUH12TN
MUH12TN -
MUH15TN MUH15TN -
MUH17TN -
MUH17TN
· Flashing of the OPERATION INDICATOR lamp (on the left-hand side)
indicates possible abnormalities.
· The OPERATION INDICATOR lamp (on the left-hand side) is lighted during
normal operation.
Indication
Outdoor unit
does not run.
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.
Outdoor unit
does not run
2.5-second OFF
MUH12TN -
U1 U2
MUH15TN -
U1 U2
U1
U1
Symptom Detect method
When the unit operates by the
remote controller or emer-
gency operation switch at 3
minutes after the main power
supply is turned on.
When serial signal from out-
door unit stops for 4 to 5 sec-
onds.
Detects Indoor coil/ room tem-
perature thermistor short or
open circuit every 8 seconds
during operation.
When rotational frequency
feedback signal is not emit
during 12-second indoor fan
operation.
When the outdoor thermistor
shorts or opens after the com-
pressor start-up.
78
Check point
Check wiring (visual check and conductiv-
ity check).
Check indoor electronic control P.C.
board.
Check outdoor DEICER P.C. board.
Check electrical parts.
Check resistance of thermistor.
Re-connect connector.
Check indoor electronic control P.C.
board.
Disconnect connector CN211 and then
check connector CN121 - to make
2
3
sure rotational frequency feedback signal
of 1.5V or over exists.
Check indoor electronic control P.C.
board.
Check indoor fan motor.
Re-connect connector.
Check deicer P.C. board.
Check resistance of thermistor.