Mitsubishi Electric MXZ-2A20NA-1 Service Manual page 51

• When thermistor is abnormal.
F F 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.
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
Gas pipe temperature (Unit A)
Gas pipe temperature (Unit B)
Gas pipe temperature (Unit C)
Ambient temperature
Fin temperature
w Except MXZ-2A20NA -
• Fan motor does not operate or stops operating shortly after starting the operation.
G G Check of outdoor fan motor
Check the connection between the
connectors CN931 and CN932.
Is the resistance between each terminal
of outdoor fan motor normal?
No
(Fixed to either 5V or 0V DC)
Replace the outdoor DC fan motor.
Symbol
RT61
RT62
RT68
w
RT6A
w
RT6B
w
RT6C
RT65
RT64
and MXZ-3A30NA - .
1 1
Yes
Disconnect CN932 from outdoor electronic control P.C. board, and
turn ON the power supply.
Rotate the outdoor fan motor manually and measure the voltage of
CN931.
Between 1(+) and 5(-)
Between 2(+) and 5(-)
Between 3(+) and 5(-)
No
Does the voltage between each terminal become 5V DC and 0V DC
repeatedly?
No
Does the outdoor fan motor rotate smoothly?
Replace the outdoor electronic control P.C. board.
Replace the thermistor except RT64.
Abnormal
In case that RT64 is abnormal, replace the
outdoor power board since RT64 is combined
with the outdoor power board.
No
Replace the outdoor electronic control
P.C. board or the outdoor power board.
Connector, Pin No.
Between CN661 pin1 and pin2
Between CN661 pin3 and pin4
Between CN661 pin7 and pin8
Between CN662 pin1 and pin2
Between CN662 pin3 and pin4
Between CN662 pin5 and pin6
Between CN663 pin1 and pin2
Between CN3 pin1 and pin2
Yes
Yes
51
Board
Outdoor electronic control P.C. board
Outdoor power board