Mitsubishi Electric MXZ-2A20NA-1, Service Manual

Page: 51 / 88

51
F F
Check of outdoor thermistors
• When thermistor is abnormal.
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
w
w
w
Except MXZ-2A20NA - and MXZ-3A30NA - .
Symbol
RT61
RT62
RT68
RT6A
RT6B
RT6C
RT65
RT64
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
Outdoor electronic control P.C. board
Outdoor power board
Board
1
1
G G
Check of outdoor fan motor
• Fan motor does not operate or stops operating shortly after starting the operation.
Yes
Yes
Yes
No
(Fixed to either 5V or 0V DC)
No
No
Check the connection between the
connectors CN931 and CN932.
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
(-)
Is the resistance between each terminal
of outdoor fan motor normal?
Does the outdoor fan motor rotate smoothly?
Does the voltage between each terminal become 5V DC and 0V DC
repeatedly?
Replace the outdoor DC fan motor. Replace the outdoor electronic control P.C. board.
Normal
Yes
No
Abnormal
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.
Disconnect the connector in the following table and
measure the resistance of the thermistor to check
whether the thermistor is normal or not.
Does the unit operate 10 minutes or more without
showing thermistor abnormality?
Replace the thermistor except RT64.
In case that RT64 is abnormal, replace the
outdoor power board since RT64 is combined
with the outdoor power board.
Normal
Replace the outdoor electronic control
P.C. board or the outdoor power board.
OB444B--2.qxp 07.4.17 4:33 PM Page 51