Troubleshooting Flow - Mitsubishi Electric MUZ-LN VG Series Service Manual

10-6. TROUBLESHOOTING FLOW

A Check of indoor fan motor
The indoor fan motor error has occurred, and the indoor fan does not operate.
Turn OFF the power supply.
Is there any foreign matter that interferes
the rotation of the line flow fan?
Yes
Remove the foreign matter and
adjust the line flow fan.
Is there 325 V DC
between CN211
and (–) ?
No
Replace the indoor power
P.C. board.
The indoor fan motor error has occurred, and the indoor fan repeats "12-second ON and 30-second OFF" 3 times, and then stops.
Measure the voltage between CN211
(+) and (–) while the fan motor is
rotating.
Replace the indoor power P.C.
board.
OBH766C
Pay enough attention to the high voltage on the fan motor connector CN211.
Turn ON the power supply, wait 5 seconds or more, and then press
EMERGENCY OPERATION switch.
Measure the supply voltage as follows within 12 seconds after EMER-
GENCY OPERATION switch is pressed.
If more than 12 seconds passes, turn OFF the power supply and turn it
ON again, then measure the voltage.
No
<Indoor power P.C. board>
1. Measure the voltage between CN211
2. Measure the voltage between CN211
<Indoor electronic control P.C. board>
3. Measure the voltage between CN102
*If more than 12 seconds pass after EMERGENCY OPERATION switch
is pressed, the voltage measured at 2. above goes 0 V DC although the
indoor P.C. board is normal.
Does the voltage between CN211
(+) and
P.C. board rise to the range of 3
(+)
Yes to 6 V DC within 12 seconds after
EMERGENCY OPERATION switch
is pressed?
Does the voltage between CN102
and GND (–) on the indoor
electronic control P.C. board fall to
Yes 2 V or less within 12 seconds after
EMERGENCY OPERATION switch
is pressed?
Is it unchanged holding 0
or 15 V DC?
Replace the indoor fan motor.
Is it unchanged holding 0
or 5 V DC?
Yes
(Unchanged)
*
(–) on the power
Yes
No
No
Measure the voltage CN102
GND (–) on the indoor electronic control
No
P.C board when the fan motor is rotating.
(Changed)
Yes
(Unchanged)
Replace the indoor
electronic control P.C.
No
board.
(Changed)
35
(+) and (–).
(+) and (–).
and GND (–).
Replace the indoor fan motor.
Replace the indoor electronic
control P.C. board.
(+) and