Mitsubishi Electronics MXZ-32SV service manual Check of thermistor

• When thermistor is abnormal. (When the LED display is a table below.)

F Check of thermistor

Start
		Abnormal
Disconnect the connector in the electronic control P. C. board (see below table), and
measure the resistance of thermistor to check whether the thermistor is normal or not.
	Normal

Replace the thermistor

Reconnect the connector (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 No thermistor abnormality is not displayed?

Yes

Normal

Replace the electronic control P. C. board.

Thermistor	Symbol	Connector, Pin No.
Defrost thermistor	RT62	Between CN661 pin1 and pin2
Discharge temperature thermistor	RT61	Between CN661 pin3 and pin4
Evaporation temperature thermistor	RT63	Between CN661 pin5 and pin6
Gas pipe temperature thermistor (Unit A)	RT66	Between CN662 pin1 and pin2
Gas pipe temperature thermistor (Unit B)	RT67	Between CN662 pin3 and pin4
Gas pipe temperature thermistor (Unit C)	RT68	Between CN662 pin5 and pin6
Gas pipe temperature thermistor (Unit D)	RT69	Between CN662 pin7 and pin8
Fin temperature thermistor	RT65	Between CN663 pin1 and pin2

• Fan motor does not operate. Or, fan motor stops at once’ after fan motor operates.

G Check of fan motor

Start

Check the connection of connector (CN851, CN852) in the fan motor relay connector and electronic control P. C. board at the noise filter P. C. board and connector (CN901, CN902) in the noise filter board.

Disconnect the fan motor connector, and measure the resistance of the		Abnormal
			Replace the fan motor
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 220V AC - 240V AC? No

Yes

1.	Turn off power supply of the indoor and outdoor unit, and disconnect the connector
		No	Replace the electronic
	(CN851, CN852).
			control P. C. board
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		No
turns on the indoor unit and EMERGENCY OPERATION starts in three minutes.
	Yes
Replace the noise filter P. C. board

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