Troubleshooting Check Table - Mitsubishi Electric Mr.Slim MSZ09UN Service Manual

1. Troubleshooting check table

• The following indication applies regardless of shape of the indicatior.
flashing
Operation Indicator
· 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.
No.
Symptom Operation indicator lamp
Outdoor unit repeated flashes
does not every 0.5 seconds
operate.
1
1-time flash
2.5 seconds OFF
2
2-time flash
2.5 seconds OFF
3
Indoor fan
motor repeats
12 seconds
ON and 3
3-time flash
minutes OFF.
4
2.5 seconds OFF
When the
indoor fan
motor breaks,
the fan keeps
stopping.
5-time flash
Outdoor unit
2.5 seconds OFF
does not
5
operate.
6-time flash
2.5 seconds OFF
6
7-time flash
2.5 seconds OFF
7
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 lighted during
normal operation.
Abnormal point
When the unit operates by the remote controller or
Mis-Wiring
emergency operation switch at 3 minutes after the main
power supply is turned on.
3 minutes after power supply turns ON, when serial signal is
not received.
Serial signal
When indoor electronic control P.C. board does not
receive serial signals from outdoor unit for 4 to 5
seconds,
Indoor coil
Indoor electronic control P.C. board constantly
thermistor
detects resistance every 8 seconds.
Auxiliary indoor
When thermistor shorts or opens.
coil thermistor
Room
temperature
thermistor
When rotational frequency feedback signal is not
Indoor fan motor
emit during 12-second indoor fan operation.
Outdoor power When compressor has stopped due to overcurrent
system protection or start-up failure protection 3 times in a
row within 1 minute after start-up.
<Thermistor short>
Outdoor
Thermistors are abnormal when they short after
thermistors
compressor start-up.
<Thermistor open>
Thermistors are abnormal when they open after
compressor start-up.
Discharge temperature thermistor is abnormal when
open circuit is detected more than 10 minutes after
compressor start-up.
Defrost thermistor is abnormal when open circuit is
detected more than 1 minutes after compressor
start-up.
When nonvolatile memory data cannot be read properly
Outdoor control
on outdoor control P.C. board, outdoor unit stops and
system
restarts 3 minutes later.
Detection method
43
Checkpoint
Refer to 'Checking
serial signal error' on
page 55.
Refer to the
characteristics of main
indoor coil thermistor,
sub indoor coil
thermistor, and room
temperature thermistor
on page 56 or 57.
Refer to G "Check of
indoor fan motor" on
page 49.
Refer to A "How to
check inverter/
compressor" on page
47.
· Shortage of
refrigerant
· Outdoor electronic
control P.C. board
Refer to J "Check
of outdoor
thermistors" on
page 51.
Replace outdoor
electronic control P.C.
board.