Mitsubishi Electric MSZ-EF18NAW-U1 Service Manual page 27

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 the 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) on the indoor
power P.C. board.
Fuse (F11)
Indoor power
P.C. board
CN211
Indoor electronic
control P.C. board
CN10A
GND(JPG)
OBH736C
Measure the resistance between
CN211 and
connector.
Measure the resistance of the vane
motor coil.
Yes
Refer to 9-5.
Replace the varistor (NR11)
and fuse (F11). 3
*
Yes
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?
Yes
Measure the resistance between
CN211 (+) and (-) of indoor fan
motor connector. 1, 2
* *
Is the resistance 1MΩ or more?
Yes
Replace the fuse (F11).
Is the resistance of
resistor (R111) approximately
3.9 Ω ?
Is there approximately 5 V DC between
5 V (+) and JPG (GND) (-) of the
indoor electronic control P.C. board?
Varistor
Is there approximately 12 V DC
(NR11)
between 12 V (+) and JPG (GND) (-)
of the indoor electronic control P.C.
board?
R111
Is connector CN102 on the
indoor electronic control P.C.
board or lead wires discon-
nected?
Replace the indoor electronic control P.C. board.
27
Short circuit:
of the indoor fan motor
Replace the indoor fan motor.
Short circuit:
Replace the vane motor and the indoor
electronic control P.C. board.
No
No
1. The fan motor connector's
*
whereas is black.
2. Connect "+" of the multimeter to fan motor connec-
*
tor's lead wire, and "-" to
the 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. *3
3
*
No
Yes
No
Yes
No
lead wire is red,
lead wire, otherwise
Replace the indoor
power P.C. board and
the indoor fan motor.
Replace the indoor fan motor.
Yes
Connect the connector or repair discon-
nection.