Mitsubishi Electronics MSH-A18ND service manual Troubleshooting check table

8-3. Troubleshooting check table

•The following indication applies regardless of shape of the indicator.

•Before taking measures, make sure that the symptom reappears for accurate troubleshooting.

When the indoor unit has started operation and the following detection method has detected an abnormality

(the first detection after the power ON), the indoor electronic control P.C. board turns OFF the indoor fan motor with the OPERATION INDICATOR lamp flashing.

Operation Indicator

Lighted Not lighted

·Flashing of the OPERATION INDICATOR lamp (on the left-hand side) indicates possible abnormalities.

·The OPERATION INDICATOR lamp (on the left-hand side) is lighting during normal operation.

No.	Abnormal	Operation indicator lamp	Symptom	Condition	Correspondence
	point
		0.5-second ON	Outdoor unit	3 minutes after power supply turns ON, when	• Refer to 8-5. D "How to check
1	Mis-Wiring		does not	serial signal is not received.	mis-wiring ".
		0.5-second OFF	operate.
	Indoor coil	2-time flash		Detect Indoor coil/room temperature	• Refer to the characteristics of
					main indoor coil thermistor,
	thermistor		Outdoor unit	thermistor short or open circuit every 8
					sub indoor coil thermistor,
2			does not	seconds during operation.
					and room temperature
	Room		operate.
					thermistor in 8-6.
	temperature	2.5-second OFF
	thermistor
		3-time flash	Indoor fan repeats	When rotational frequency feedback signal is	• Refer to 8-5. A "Check of
	Indoor fan		12 seconds ON		indoor fan motor".
3			and 3minutes OFF.	not emitting during 12-second indoor fan
	motor		When the indoor	operation.
		2.5-second OFF	fan breaks, the fan
			keeps stopping.
	Indoor	4-time flash	Outdoor unit	When it cannot properly read data in the	• Check the indoor electronic
				nonvolatile memory of the indoor electronic	control P.C. board.
			does not
4	control			control P.C. board.
			operate.
	system
		2.5-second OFF
				<Thermistor short>	• Shortage of refrigerant
		6-time flash		Thermistors are abnormal when they short	• Check the deicer P.C.
				after compressor start-up.	board.
5	Outdoor		Outdoor unit	<Thermistor open>	Refer to "Check of outdoor
	thermistor			Thermistors are abnormal when they open	thermistor".
			does not
				after compressor start-up.	Refer to outdoor unit service
		2.5-second OFF	operate.
				However, discharge temperature thermistor is	manual.
				abnormal when open circuit is detected more
				than 10 minutes after compressor start-up.
	Outdoor	7-time flash	Outdoor unit	When it cannot properly read data in the	• Check the deicer P.C. board.
				nonvolatile memory of the deicer P.C. board,	Refer to outdoor unit service
	control
6			does not	outdoor unit stops.	manual.
	system
			operate.
		2.5-second OFF

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