Mitsubishi Electric MXZ-2C20NA2 Service Manual page 125

• 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 12-7.)
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
Thermistor
Defrost
Discharge temperature
Outdoor heat exchanger temperature
Ambient temperature
Fin temperature
OBH702N
(MXZ-3C24/3C30/4C36NA, MXZ-3C24/3C30/4C36NA2,
MXZ-3C24/3C30/4C36NA3, MXZ-3C24/3C30/4C36NA4)
Abnormal
(MXZ-5C42NA, MXZ-2C20/5C42NA2,
MXZ-2C20/5C42NA3, MXZ-2C20/5C42NA4,
MXZ-2C20/3C24/3C30NAHZ, MXZ-2C20/3C24/3C30NAHZ2,
MXZ-2C20/3C24/3C30NAHZ3, MXZ-2C20/3C24/3C30NAHZ4)
Replace the thermistor except RT64.
If RT64 is abnormal, replace the outdoor power
P.C. board since RT64 is combined with this board.
Replace the outdoor control P.C. board or the
outdoor power P.C. board.
No
Symbol Connector, Pin No.
RT61 Between CNTH1 pin1 and pin2
RT62 Between CNTH1 pin3 and pin4
RT68 Between CNTH1 pin7 and pin8
RT65 Between CNTH2 pin1 and pin2
Between CN171 pin1 and pin2
RT64
125
Replace the thermistor.
Board
Outdoor control P.C. board
Outdoor power P.C. board