Mitsubishi Electric MSH-A18ND-S1 Service Manual page 14

8-5. Troubleshooting flow
When OPERATION INDICATOR lamp flashes 3-time.
Indoor fan motor doesn't operate.
A Check of indoor fan motor
No
Are lead wires connected?
Reconnect the lead wires.
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.
Indoor unit operates by pressing the EMERGENCY OPERATION switch, but doesn't operate with the remote controller.
Check of remote controller and receiver P.C. board
B
w Check 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
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Turn OFF the power supply.
Check connector CN211 visually.
Yes
Is resistance 0 (short circuit) or ∞ (open circuit)?
Yes ( 0 or ∞ )
Repair or replace the indoor fan motor.
No
Replace the batteries.(Refer to 8-1.4.)
(not clear)
Turn on a radio to AM and press
No
OPERATE/STOP(ON/OFF) button on the
remote controller.
Is noise heard from radio?
Yes
Are there any fluorescent lights of
inverter or rapid-start type within
the range of 1m?
No
Measure the voltage between receiver P.C. board connector CN301 No.1(+) and No.3(-) when the remote
controller button is pressed.
Is the voltage approx. 4V DC?
No(5V or 0V DC)
Replace the receiver P.C. board.
14
Is soldered point of the connector
correctly soldered?
Yes
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
No
voltage between No.2(+) and No.3(-) on CN121.
(others)
No
Does voltage repeat 0V DC and 5V DC?
Replace the indoor electronic control P.C. board.
No
Yes
Reinstall the unit away from lights.
Attach a filter on receiving part.
Yes
Replace the indoor electronic control P.C.
board.
No
Resolder it.
Yes
Replace the remote controller.