Mitsubishi Electronics service manual Troubleshooting check table MUZ-GB50VA

10-4. Troubleshooting check table MUZ-GB50VA

No.	Symptom	Indication		Abnormal point / Condition	Condition	Correspondence
		LED1(Red)	LED2(Yellow)
	Outdoor unit				When over current protection stop is continuously	• Check the connection of the compressor connecting
	does not
					performed three times within 1 minute after the compressor gets	wire.
	operate.
1		Lightning	Twice	Outdoor power system	started, or when converter protection stop or bus-bar voltage	• Refer to 10-6.A"How to check inverter/compressor".
					protection stop is continuously performed three times within 3	• Check the stop valve.
					minutes after start-up.
				Discharge temperature	When a short circuit is detected in the thermistor during operation, or	• Refer to 10-6.B"Check of outdoor thirmistors".
2		Lightning	3 times		when an open circuit is detected in the thermistor after 10 minutes
				thermistor
					of compressor start-up.
				Fin temperature		• Refer to 10-6.B"Check of outdoor thirmistors".
				thermistor	When a short or open circuit is detected in the thermistor during
3		Lightning	4 times
				P.C board temperature	operation.
						• Replace the outdoor electronic control P.C. board.
				thermistor
				Ambient temperature	When a short or open circuit is detected in the thermistor during
				thermistor	operation.
				Outdoor heat exchanger	When a short circuit is detected in the thermistor during operation, or
					when an open circuit is detected in the thermistor after 5 minutes (in
4				temperature thermistor
		Lightning	5 times		cooling) and 10 minutes (in heating) of compressor start-up.	• Refer to 10-6.B"Check of outdoor thirmistors".
					When a short circuit is detected in the thermistor during operation, or
				Defrost thermistor	when an open circuit is detected in the thermistor after 5 minutes of
					compressor start-up.
5		Lightning	6 times	Serial signal	When the communication fails between the indoor and outdoor	• Refer to 10-6.H"How to check mis-wiring and serial signal
					unit for 3 minutes.	error.
6		Lightning	7 times	Nonvolatile memory data	When the nonvolatile memory data cannot be read properly.	• Replace the outdoor electronic control P.C. board.
7		Lightning	8 times	Current sensor	Current sensor protection stop is continuously performed twice.	• Replace the power board.
8		Lightning	11 times	Communication error	When the communication protection stop between boards is	• Check the connecting wire between outdoor electronic control
				between P.C. boards	continuously performed twice.	P.C. board and power board.
9		Lightning	12 times	Zero cross detecting	The protection stop of the zero cross detecting circuit is continuously	• Check the connecting wire among outdoor electronic control
				circuit	performed 10 times.	P.C. board, noise filter P.C. board and power board.
	'Outdoor unit					• Reconnect compressor connector.
	stops and			IPM protection	When over-current is detected after 30 minutes of compressor start-up.
	restarts 3					• Refer to 10-6.A"How to check inverter/compressor".
10	minutes	Twice	Goes out			• Check the stop valve.
					When over-current is detected within 30 minutes of compressor
	later' is					• Check the power module (PAM module).
	repeated.			Lock protection	start-up
		3 times	Goes out	Discharge temperature	When discharge temperature exceeds 116:during operation.	• Check the amount of gas and refrigerant circuit.
11				protection	compressor stops. Compressor can restart if discharge temperature	• Refer to 10-6.G"Check of LEV".
					thermistor reads 100: or less 3 minutes later.
				Fin temperature	When the fin temperature exceeds 87: during operation.	•Check refrigerant circuit and refrigerant amount.
				protection
12		4 times	Goes out			•Refer to 10-6.D"Check of outdoor fan motor".
				P.C. board temperature	When the P.C. board temperature exceeds 70: during operation.
				protection
				High-pressure	When the outdoor heat exchanger temperature exceeds 70:	• Check around of gas and the refrigerant circuit.
				protection	during cooling or when indoor gas pipe temperature exceeds 70:	• Check of stop valve.
13		5 times	Goes out		during heating.
14		8 times	Goes out	Converter protection	When a failure is detected in the operation of the converter during	• Replace the power board.
					operation.
				Bus-bar voltage	When the bus-bar voltage exceeds 400V or falls to 200V or below
15		9 times	Goes out	protection (1)	during compressor operating.	• Replace the power board.
				Bus-bar voltage	When the bus-bar voltage exceeds 400V or falls to 50V or below
				protection (2)	during compressor operating.
16		13 times	Goes out	Outdoor fan motor	When failure occurs continuously three times within 30 seconds after	• Refer to 10-6.D"Check of outdoor fan motor".
					the fan gets started.
17		Lighting	8 times	Current sensor	When a short or open circuit is detected in the current sensor during	• Replace the power board.
				protection	compressor operating.
18		Lighting	11 times	Communication between P.C.	Communication error occurs between the outdoor electronic control P.C.	• Check the connecting wire between outdoor electronic control
				boards protection	board and power board for more than 10 seconds.	P.C. board and power board.
19		Lighting	12 times	Zero cross detecting circuit	When zero cross signal cannot be detected while the compressor is	• Check the connecting wire among outdoor electronic control
				protection	operating.	P.C. board, noise filter P.C. board and power board.

NOTE 1. The location of LED is illustrated at the right figure. Refer to 10-7.1. 2. LED is lighted during normal operation.

The flashing frequency shows the number of times the LED blinks after every 2.5-second OFF. (Example) When the flashing frequency is “2”.

0.5-second ON

ON

2.5-second OFF 2.5-second OFF

OFF

Outdoor electronic control P.C. board(Parts side)

LED2 LED1

Lighting

0.5-second ON

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