Mitsubishi Electronics MSH-A18ND service manual Check of indoor fan motor

8-5. Troubleshooting flow

When OPERATION INDICATOR lamp flashes 3-time.

Indoor fan motor doesn’t operate.

A Check of indoor fan motor		Turn OFF the power supply.
		Check connector CN211 visually.
No			Yes	Is soldered point of the connector		No
	Are lead wires connected?
				correctly soldered?
					Yes
Reconnect the lead wires.

Resolder it.

Disconnect lead wires from connector CN211 on the indoor electronic control P.C. board. Measure resistance between lead wires No.3 and No.4 and then No.1 and No.4.

Is resistance 0 (short circuit) or ∞ (open circuit)?

Yes ( 0 or ∞ )

Repair or replace the indoor fan motor.

No

(others)

Turn ON the power supply. Stop it if the unit operate. Insert screwdriver into air outlet to rotate indoor fan motor slowly for 1 revolution or over, and measure voltage between No.2(+) and No.3(-) on CN121.

No

Does voltage repeat 0V DC and 5V DC?

Yes

Replace the indoor electronic control P.C. board.

Indoor unit operates by pressing the EMERGENCY OPERATION switch, but doesn’t operate with the remote controller.

B Check of remote controller and receiver P.C. board

wCheck if the remote controller is exclusive for this air conditioner.

Press OPERATE/STOP(ON/OFF) button on the remote controller.

Is LCD display on the the remote controller visible?

Yes

Remove the batteries, then set them back and press the RESET button. Check if the unit operates with the remote controller.

Does the unit operate with the remote controller?

Yes

OK

No

Replace the batteries.(Refer to 8-1.4.)

(not clear)

No	Turn on a radio to AM and press
	OPERATE/STOP(ON/OFF) button on the
	remote controller.

Is noise heard from radio?		No
	Yes
Are there any fluorescent lights of		Yes
inverter or rapid-start type within
the range of 1m?
	No

Replace the remote controller.

●Reinstall the unit away from lights.

●Attach a filter on receiving part.

Measure the voltage between receiver P.C. board connector CN301 No.1(+) and No.3(-) when the remote controller button is pressed.

Yes

Is the voltage approx. 4V DC?

No(5V or 0V DC)

Replace the indoor electronic control P.C. board.

Replace the receiver P.C. board.

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