Mitsubishi Electric MS-A18VD-K1 Service Manual page 16

8-5. Troubleshooting flow
When OPERATION INDICATOR lamp flashes 3-time.
Indoor fan motor does not operate.
A 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.1 and No.4 and then No.3 and No.4.
Indoor unit operates by pressing the EMERGENCY OPERATION switch, but does not operate with the remote controller.
B B Check of remote controller and receiver P.C. board
w Check if the remote controller is exclusive for this air conditioner.
Switch on the remote controller.
Is LCD display on the remote con-
troller visible?
Yes
Remove batteries, then set them back and
press the RESET button.
Check if the unit operates with remote con-
troller.
Does the unit operate with remote
controller?
Yes
OK
Measure the voltage between receiver P.C. board connector CN301 No.1
the remote controller button is pressed (Refer to 8-6.).
OB400C
Turn OFF the power supply.
Check connector CN211 visually.
Yes
Is resistance 0 (short circuit) or ∞ (open circuit)?
Yes ( 0 or ∞ )
Repair the indoor fan motor.
No
Replace the batteries
(Refer to 8-1.4.).
(not clear)
No
Turn on a radio to AM and press switch on
the remote controller.
Is noise heard from radio?
Are there any fluorescent lights of
inverter or rapid-start type within the
range of 1m?
Is the voltage approximately 4 VDC?
Replace the receiver P.C.board.
Is soldered point of the connector
Turn ON the power supply.
Stop it if the unit operate. Insert screwdriver into
air outlet to rotate indoor fan motor slowly for 1
No
revolution or over, and measure voltage No.2(+)
(others)
and No.3(-) on CN121.
No
Replace the indoor electronic control P.C. board.
No
Yes
Yes
No
+
( )
and No.3
Yes
No (5V or 0 VDC)
16
No
correctly soldered?
Yes
Resolder it.
Does voltage repeat 0 VDC and 5 VDC?
Yes
Replace the remote controller.
Reinstall the unit away from lights.
Attach a filter on receiving part.
-
( )
when
Replace the indoor electronic control
P.C. board