Mitsubishi Electric MXZ-3C54VA Service Manual page 69

• When thermistor is abnormal.
Check of outdoor thermistors
Disconnect the connector in the following table and measure
the resistance of the thermistor to check whether the thermistor
is normal or not. (Refer to 11-7.)
Normal
Reconnect the connector in the following table and
disconnect the lead wire leading to the compressor.
3 minutes after turning ON the power supply,
start EMERGENCY OPERATION.
Does the unit operate 10 minutes or more without
showing thermistor abnormality?
Yes
Normal
MXZ-3C54/3C68/4C71/4C80/5C100VA
Thermistor
Defrost
Discharge temperature
Outdoor heat exchanger temperature
Ambient temperature
Fin temperature
MXZ-6C120VA
Thermistor
Defrost
Discharge temperature
Outdoor heat exchanger temperature
Ambient temperature
Abnormal
Replace the outdoor electronic control
No
P.C. board, outdoor control P.C. board or
the outdoor power board.
Symbol Connector, Pin No.
Between CN661 pin1 and pin2
RT61
RT62 Between CN661 pin3 and pin4
RT68 Between CN661 pin7 and pin8
Between CN663 pin1 and pin2
RT65
RT64 Between CN3 pin1 and pin2
Symbol Connector, Pin No.
RT61 Between CN661 pin1 and pin2
Between CN661 pin3 and pin4
RT62
RT68 Between CN661 pin5 and pin6
Between CN663 pin1 and pin2
RT65
69
Replace the thermistor except RT64.
In case that RT64 is abnormal,
replace the outdoor power board
since RT64 is combined with this
board.
Board
Outdoor electronic control P.C. board
Outdoor power board
Board
Outdoor control P.C. board