Mitsumi electronic Comprehensive Guide for Self-Diagnosis of Mitsumi Air Conditioner Models

9-3. SELF-DIAGNOSIS ACTION TABLE

Note: Refer to the manual of outdoor unit for the details of display such as F, U, and other E.

Error Code	Abnormal point and detection method	Cause		Countermeasure
	Room temperature thermistor (TH1)	Defective thermistor	– Check resistance value of thermistor.
	The unit is in 3-minute resume	characteristics	0	• • • • • • • • • • 15.0k
	prevention mode if short/open of	Contact failure of connector	10	• • • • • • • • • • • • 9.6k
	thermistor is detected. Abnormal if the	(CN20) on the indoor controller	20	• • • • • • • • • • • • 6.3k
	unit does not reset normally after 3 min-	board (Insert failure)	30	• • • • • • • • • • • • 4.3k
	utes. (The unit returns to normal opera-	Breaking of wire or contact	40	• • • • • • • • • • •3.0k
	tion, if it has been reset normally.)	failure of thermistor wiring	If you put force on (draw or bend) the lead wire
	Constantly detected during cooling,	Defective indoor controller	while measuring resistance value of thermistor,
	drying, and heating operation.	board	breaking of wire or contact failure can be
	Short: 90		detected.
P1	Open: -40		Check contact failure of connector (CN20) on
			the indoor controller board. Refer to 9-7.
			Turn the power on again and check restart
			after inserting connector again.
			Check room temperature display on remote
			controller.
			Replace indoor controller board if there is
			abnormal difference with actual room
			temperature.
			Turn the power off, and on again to operate
			after check.
	Pipe temperature thermistor/Liquid	Defective thermistor	– Check resistance value of thermistor.
	(TH2)	characteristics	For characteristics, refer to (P1) above.
	The unit is in 3-minute resume	Contact failure of connector	Check contact failure of connector (CN44) on
	prevention mode if short/open of	(CN44) on the indoor controller	the indoor controller board. Refer to 9-7.
	thermistor is detected. Abnormal if the	board (Insert failure)	Turn the power on and check restart after
	unit does not reset normally after 3 min-	Breaking of wire or contact	inserting connector again.
	utes. (The unit returns to normal opera-	failure of thermistor wiring	Check pipe <liquid> temperature with remote
	tion, if it has been reset normally.)	Defective refrigerant circuit is	controller in test run mode. If pipe <liquid>
P2	Constantly detected during cooling,	causing thermistor tempera-	temperature is extremely low (in cooling
	drying, and heating (except defrosting)	ture of 90	mode) or high (in heating mode), refrigerant
	operation.	-40	circuit may have defect.
	Short: 90	Defective indoor controller	Check pipe <liquid> temperature with remote
	Open: -40	board	controller in test run mode. If there is extremely
			difference with actual pipe <liquid> temperature,
			replace indoor controller board.
			Turn the power off, and on again to operate
			after check.
	Contact failure of drain float switch (CN4F)	Contact failure of connector	Check contact failure of float switch connec-
	Extract when the connector of drain float	(Insert failure)	tor.
P4	switch is disconnected.		Turn the power on again and check after
	( and of connector CN4F is not		inserting connector again.
(5701)
	short-circuited.)	Defective indoor controller	Operate with connector (CN4F) short-circuited.
	Constantly detected during operation.	board	Replace indoor controller board if abnormality
			reappears.
	Drain overflow protection operation	Malfunction of drain pump	Check if drain pump works.
	Suspensive abnormality, if drain float	Defective drain	Check drain function.
	switch is detected to be underwater for	Clogged drain pump
	1 minute and 30 seconds continuously	Clogged drain pipe
	with drain pump on.	Defective drain float switch	Remove drain float switch connector CN4F
	Turn off compressor and indoor fan.	Catch of drain float switch or	and check if it is short (Switch On) with the
	Drain pump is abnormal if the condition	malfunction of moving parts	moving part of float switch UP, or OPEN with
	above is detected during suspensive	cause drain float switch to be	the moving part of float switch down.
	abnormality.	detected under water (Switch	Replace float switch if it is short with the
P5	Constantly detected during drain pump	On)	moving part of float switch down.
	operation.	Defective indoor-controller	Replace indoor controller board if it is short-
		board	circuited between -		of the drain float
			switch connector CN4F and abnormality
			reappears.
			It is not abnormal if there is no problem about
			the above-mentioned		~
			Turn the power off, and on again to operate
			after check.

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