Mitsubishi Electric MUZ-LN VG Series Service Manual page 37

C Check of indoor P.C. board and indoor fan motor
Turn OFF the power supply.
Remove indoor fan motor connector CN211
from indoor power P.C. board and vane
motor connector CN151 from the indoor
electronic control P.C. board and turn ON
the power supply.
Does the unit operate with the remote
controller?
Does OPERATION INDICATOR lamp light
up by pressing EMERGENCY OPERATION
switch?
No
Turn OFF the power supply.
Check both "parts side" and "pattern
side" of the indoor power P.C. board
visually.
Measure the resistance of resistor
(R111) [MSZ-LN18/25/35/60]/reactor
(L112) [MSZ-LN50] on the indoor power
P.C. board.
Indoor power Fuse (F11)
P.C. board
CN211
Indoor electronic
control P.C. board
OBH766C
Measure the resistance of indoor fan
motor.
Refer to 10-5.
Measure the resistance of the vane
motor coil.
Yes
Refer to 10-5.
Measure the resistance of the i-see
SENSOR MOTOR coil. Refer 10-5.
Replace the varistor (NR11)
and fuse (F11).
Are the varistor (NR11)
burnt and the fuse (F11)
blown?
Be sure to check both the fuse
and the varistor in any case.
Is the fuse (F11) blown
only?
Measure the resistance between
CN211 (+) and
motor connector.
Is the resistance 1 MΩ or
more?
Replace the fuse (F11).
Varistor
(NR11)
R111
L112
CN102
Replace the indoor electronic control P.C. board.
GND
3
*
Yes
No
No
Yes
1. The fan motor connector's
*
whereas
2. Connect "+" of the tester to fan motor connector's
*
lead wire, and "-" to
(-) of indoor fan
1, 2 resistance cannot be measured properly.
* *
3. Please replace the fuse after removing the indoor
*
power P.C. board from the electrical box.
Replace the fuse (F11) and the
No indoor fan motor.
Yes
3
*
Is the resistance of resistor (R111)
[MSZ-LN18/25/35/60]/reactor
(L112) [MSZ-LN50] approximately
3.9 Ω?
Yes
Is there approximately 5 V DC
between 5 V (+) and GND (-) of the
indoor electronic control P.C. board?
Is there approximately 12 V DC
between 12 V (+) and GND (-) of the
indoor electronic control P.C. board?
No
Are connector CN102 on the
indoor electronic control P.C.
board or lead wires discon-
nected?
No
37
Short circuit:
Replace the indoor fan motor.
Short circuit:
Replace the vane motor and the indoor
electronic control P.C. board.
Short circuit
Replace the i-see SENSOR MOTOR and
the indoor electronic P.C. board.
lead wire is red,
is black.
lead wire, otherwise the
3
*
Replace the indoor
power P.C. board and
No
the indoor fan motor.
Replace the indoor fan motor.
Yes
Connect the connector or repair discon-
Yes nection.