Mitsubishi Electric MXZ-24UV -E2 Service Manual page 31

• When thermistor is abnormal. (When the LED display is a table below.)
F F Check of thermistor
LED Thermistor
E7 Defrost thermistor
E6 Discharge temperature thermistor
E9 Evaporation temperature thermistor
F5 Gas pipe temperature thermistor (Unit A)
F6 Gas pipe temperature thermistor (Unit B)
F7 Gas pipe temperature thermistor (Unit C)
d4 Fin temperature thermistor
Start
Disconnect the connector in the electronic control P. C. board (see above table), and
measure the resistance of thermistor to check whether the thermistor is normal or not.
Normal
Reconnect the connectors (CN661, CN662 and CN663) and disconnect the lead wire leading to the compressor.
Turn on power supply to the indoor and outdoor unit. Three minutes later EMERGENCY OPERATION starts.
Does thermistor operate 10 minutes or more though the
thermistor abnormality is not displayed?
Yes
Normal
• Fan motor does not operate. Or, fan motor stops at once' after fan motor operates.
G G Check of fan motor
Start
Check the connection of fan motor connector, connectors (CN851, CN852) on electronic control P.C. board,
and connectors (CN901, CN902) on noise filter P.C. board.
Disconnect the fan motor connector, and measure the resistance of the
fan motor winding to check the winding characteristic.
Normal
1. Disconnect the lead wire leading to the compressor. Turn on power supply to the
indoor and outdoor unit. Three minutes later, EMERGENCY OPERATION starts.
2. Check the voltage between pin 2 and pin 3, pin 2 and pin 5, pin 2 and pin 6 at the fan motor connector.
Is there voltage of 230V AC?
No
1. Turn off power supply of the indoor and outdoor unit, and disconnect the connector
(CN851, CN852).
2. Is the voltage 0V, when the voltage between CN852 pin1 (+) and CN851 pin1 (-),
pin2 (-), or pin3 (-) are measured after the power supply is turned on the outdoor unit?
Yes
Is there voltage of 12V DC between CN852 pin1 (+) and pin3 (-), when power supply
turns on the indoor unit and EMERGENCY OPERATION starts in three minutes?
Yes
Replace the noise filter P. C. board.
Symbol
RT62
RT61
RT63
RT66
RT67
RT68
RT65
No
Replace the electronic
control P. C. board.
Yes
31
Connector, Pin No.
Between CN661 pin1 and pin2
Between CN661 pin3 and pin4
Between CN661 pin5 and pin6
Between CN662 pin1 and pin2
Between CN662 pin3 and pin4
Between CN662 pin5 and pin6
Between CN663 pin1 and pin2
Abnormal
Abnormal
No
No
Replace the thermistor.
Replace the fan motor.
Replace the electronic
control P. C. board.