Check Of Outdoor Thermistors; Check Of Outdoor Fan Motor - Mitsubishi Electric MXZ-2B20NA Service Manual

• 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-2B20NA MXZ-3B24NA MXZ-3B30NA MXZ-4B36NA
Thermistor
Defrost
Discharge temperature
Outdoor heat exchanger temperature
Ambient temperature
Fin temperature
MXZ-5B42NA
Thermistor
Defrost
Discharge temperature
Outdoor heat exchanger temperature
Ambient temperature
• Fan motor does not operate or stops operating shortly after starting the operation.

Check of outdoor fan motor

MXZ-2B20NA MXZ-3B24NA MXZ-3B30NA MXZ-4B36NA
Disconnect CN932 from the outdoor
electronic control P.C. board, and measure
the resistance of the outdoor fan motor.
Is the resistance of outdoor fan motor
normal? (Refer to 11-5.)
No
(Fixed to either 5 V or 0 V DC)
Replace the outdoor fan motor.
OBH560G
Abnormal
No
Replace the electronic control P.C. board/outdoor
control P.C. board or the 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
RT65 Between CN663 pin1 and pin2
Turn ON the power supply.
Yes
Rotate the outdoor fan motor manually and measure the voltage of
CN931.
Between (+) and
Between (+) and
Between (+) and
No
Does the voltage between each terminal become 5 V DC and 0 V DC
repeatedly ?
No
Does the outdoor fan motor rotate smoothly ?
Replace the electronic control P.C. board.
72
Replace the thermistor except RT64.
In case that RT64 is abnormal, replace the
power board since RT64 is combined
with the power board.
Electronic control P.C. board
Power board
Outdoor control P.C. board
(-)
(-)
(-)
Yes
Yes
Board
Board