Mitsubishi Electric NTXMMX A AA Series Service Manual page 31

The unit cannot be operated with the remote controller.
Also, OPERATION INDICATOR lamp does not light up by pressing the emergency operation switch.
Check of indoor electronic control P.C. board and indoor fan motor
C
Turn OFF the power supply.
Remove indoor fan motor connector CN211 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 electronic control P.C.
board visually.
Indoor electronic
control P.C. Board
R111
C111
VARISTOR (NR11)
CN211 CN151
OBHT802B
Turn OFF the power supply.
Measure the resistance between CN211
and
Yes
Turn OFF the power supply.
Measure the resistance of the horizontal vane
motor coil and the vertical vane motor coil.
Refer to 9-5.
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
(+) and
motor connector (to CN211 on the
indoor electronic control P.C. board).
*1, *2
Is the resistance 1MΩ
or more?
Replace the fuse (F11).
Measure the cement resistance R111 on
the indoor electronic control P.C. board.
Fuse (F11)
of the indoor fan motor connector.
Yes
No
No
Yes
(-) of the indoor fan *1. The fan motor connector's
*2. Connect "+" of the tester to fan motor connector's
wire, and "-" to
measured properly.
Replace the fuse (F11) and the indoor fan motor.
No
Yes
Is the resistance
approximately 4Ω?
Yes
Replace the indoor electronic control P.C. board.
31
Short/ open circuit:
Replace the indoor fan motor.
Short/ open circuit:
Replace the horizontal vane motor, the vertical
vane motor coil and the indoor electronic
control P.C. board.
lead wire is red, whereas
lead wire, otherwise the resistance cannot be
Replace the indoor electronic control P.C. board
and the indoor fan motor.
No
is black.
lead