Mitsubishi Electronics PUY-A18NHA2 Case Judgment and action Open/short circuit of discharge

Error Code		Abnormal point and detection method		Case			Judgment and action
	Open/short circuit of discharge			1 Disconnection or contact			1 Check connection of connector (TH4) on the
	temperature thermistor (TH4)			failure of connector (TH4) on			outdoor controller circuit board.
	Abnormal if open (3: [37˚F] or less) or			the outdoor controller circuit			Check breaking of the lead wire for
	short (217: [422˚F] or more) is detected			board			thermistor (TH4). Refer to 10-9.
	during compressor operation.			2 Defective thermistor			2 Check resistance value of thermistor (TH4) or
U3	(Detection is inoperative for 10 minutes of			3 Defective outdoor controller			temperature by microcomputer.
							(Thermistor/TH4: Refer to 10-6.)
	compressor starting process and for 10			circuit board
(5104)
							(SW2 on A-Control Service Tool: Refer to 10-
	minutes after and during defrosting.)
							10.)
							3 Replace outdoor controller board.
	Open/short of outdoor unit thermistors			1 Disconnection or contact failure			1 Check connection of connector (TH3,TH6/TH7)
	(TH3, TH6, TH7, and TH8)			of connectors		)	on the outdoor controller circuit board.
	Abnormal if open or short is detected			Outdoor controller circuit			Check connection of connector (CN3) on the
	during compressor operation.			board: TH3,TH6/TH7			outdoor power circuit board.
	Open detection of thermistors TH3 and			Outdoor power circuit board:			Check breaking of the lead wire for thermistor
	TH6 is inoperative for 10 seconds to 10			(CN3			(TH3,TH6,TH7,TH8). Refer to 10-9.
	minutes after compressor starting and 10			2 Defective thermistor			2 Check resistance value of thermistor
	minutes after and during defrosting.			3 Defective outdoor controller			(TH3,TH6,TH7,TH8) or check temperature by
	WCheck which unit has abnormality in its			circuit board			microcomputer.
		thermistor by switching the mode of					(Thermistor / TH3, TH6, TH7, TH8 : Refer to 10-6.)
U4		SW2. (PAC-SK52ST)					(SW2 on A-Control Service Tool: Refer to 10-
		(Refer to 10-10.)					10.)
(TH3:5105)
							3 Replace outdoor controller circuit board.
(TH6:5107)							WEmergency operation is available in case of
(TH7:5106)							abnormalities of TH3, TH6 and TH7.
(TH8:5110)							Refer to 10-8.
			Thermistors			Open detection		Short detection
		Symbol	Name
		TH3	Thermistor <Outdoor pipe>		– 40:[-40˚F] or below			90:[194˚F] or above
		TH6	Thermistor <Outdoor 2-phase pipe>		– 40:[-40˚F] or below			90:[194˚F] or above
		TH7	Thermistor <Outdoor>		– 40:[-40˚F] or below			90:[194˚F] or above
		TH8	Thermistor <Heatsink>		– 27:[-17˚F] or below			102:[216˚F] or above
	Temperature of heatsink			1 The outdoor fan motor is			12 Check outdoor fan.
	Abnormal if heat sink thermistor(TH8)			locked.
	detects temperature indicated below.			2 Failure of outdoor fan motor			3 Check airflow path for cooling.
	A12, 18, 42N··············84:, 183˚F			3 Air flow path is clogged.
	A24, 30, 36N··············81:, 177˚F			4 Rise of ambient temperature			4 Check if there is something which causes
				5 Defective thermistor			temperature rise around outdoor unit.
				6 Defective input circuit of			(Upper limit of ambient temperature is 46:
				outdoor power circuit board			[114˚F].)
				7 Failure of outdoor fan drive			Turn off power, and on again to check if U5
							is displayed within 30 minutes.
U5				circuit
							If U4 is displayed instead of U5, follow the
(4230)
							action to be taken for U4.
							5 Check resistance value of thermistor (TH8)
							or temperature by microcomputer.
							(Thermistor/TH8: Refer to 10-6.)
							(SW2 on A-Control Service Tool: Refer to 10-
							10.)
							6 Replace outdoor power circuit board.
							7 Replace outdoor controller circuit board.
	Power module			1 Outdoor stop valve is closed.			1 Open stop valve.
	Check abnormality by driving power module			2 Decrease of power supply voltage			2 Check facility of power supply.
	in case overcurrent is detected.			3 Looseness, disconnection or			3 Correct the wiring (U·V·W phase) to
U6	(UF or UP error condition)			converse of compressor wiring			compressor. Refer to 10-9 (Outdoor power
(4250)				connection			circuit board).
				4 Defective compressor			4 Check compressor referring to 10-6.

5Defective outdoor power circuit 5 Replace outdoor power circuit board. board

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