Mitsubishi Electric MSH-18RV Service Manual page 56

MSH-24/30RV
• The following indication does not depend on the shape of lamp.
flashing
Operation Indicator
Before taking measures, make sure that the symptom reappears, for accurate troubleshooting.
Self check table
Abnormal
No. Operation indicator lamp
point
0.5-second ON
1 Mis-Wiring
0.5-second OFF
1-time flash
Serial sig-
nal
MSH-24RV
only
2.5-second OFF
Indoor coil
2-time flash
thermistor
2
Room
2.5-second OFF
tempera-
ture
thermistor
3-time flash
Indoor fan
3 motor
2.5-second OFF
Indoor
4-time flash
control
4
system
MSH-30RV
only
2.5-second OFF
6-time flash
Outdoor
5
thermistor
7-time flash
Outdoor
6
control
system
10-time flash
Low
discharge
temperature
7
protection
MSH-30RV
only
2.5-second OFF
NOTE : When the indoor unit has started operation and the above 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.
· Flashing of the OPERATION INDICATOR lamp (on the left-hand side) indicates possible
abnormalities.
· The OPERATION INDICATOR lamp (on the left-hand side) is lighting during normal operation.
Symptom
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
Indoor fan
repeats 12
seconds ON
and 3
minutes
OFF.
When the
indoor fan
breaks, the
fan keeps
stopping.
Outdoor unit
does not
operate.
Outdoor unit
does not
operate.
2.5-second OFF
Outdoor unit
does not
operate.
2.5-second OFF
Outdoor unit
does not
operate.
Detection method
3 minutes after power supply turns ON, when
serial signal is not received.
When serial signal from outdoor unit stops for
4 to 5 seconds.
Detect Indoor coil/room temperature
thermistor short or open circuit every 8
seconds during operation.
When rotational frequency feedback signal is
not emitting during 12-second indoor fan
operation.
When 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.
When it cannot properly read data in the
nonvolatile memory of the deicer P.C. board,
outdoor unit stops [and restarts 3 minutes
later(MSH-24RV only).]
When discharge temperature has been 50:
or less on cool operation, or has been 49: or
less on heat operation for 20 minutes.
56
Checkpoint
• Refer to H "How to check
mis-wiring " on page 65.
• Refer to G "How to check
mis-wiring and serial signal
error" on page 64.
• Refer to the characteristics of
main indoor coil thermistor,
sub indoor coil thermistor,
and room temperature
thermistor on page 67 or 68.
• Refer to A "Check of
indoor fan motor" on page 59.
• Replace the indoor electronic
control P.C. board.
• Shortage of refrigerant
• Replace the deicer P.C.
board.
Refer to J "Check of outdoor
thermistor" on page 66.
• Replace the deicer P.C.
board.
• Refer to I "Check of LEV" on
page 66.
• Check refrigerant circuit and
refrigerant amount.