Mitsubishi Electric MSZ-DM25VA Service Manual page 24

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.
1. The fan motor connector's lead wire is red,
whereas is black.
2. Connect "+" of the tester to fan motor
connector's lead wire, and "-" to
otherwise the resistance cannot be measured
properly.
3. Please replace the fuse after removing the
indoor power P.C. board from the electrical
box.
Measure the resistance of resistor (R111)
on the indoor power P.C. board.
Indoor electronic control
P.C. board
12 VDC
Indoor power P.C. board
OBH750
Measure the resistance of indoor fan
motor.
Refer to 10-5.
Measure the resistance of the vane
motor coil.
Yes
Refer to 10-5.
Replace the varistor (NR11)
and fuse (F11). 3
Is 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
lead wire,
motor connector. 1, 2
Is the resistance 1MΩ or more?
Replace the fuse (F11). 3
GND
CN10A
5 VDC
Replace the indoor electronic control P.C. board.
R111
CN211
Yes
No
With a tester, check the
continuity between the
connector CN201
indoor control P.C. board and
S2 on the terminal block.
No
Yes
(-) of indoor fan
Replace the fuse (F11) and the
indoor fan motor. 3
No
Yes
Is the resistance of resistor (R111)
approximately 4 Ω ?
Yes
Is there approximately 5 VDC between
5 V (+) and GND (-) of the indoor
electronic control P.C. board? Is there
approximately 9 V to 13 VDC between
12 V (+) and GND (-) of the indoor
electronic control P.C. board?
No
Is the connector CN10A on
the indoor electronic control
P.C. board or lead wires
disconnected?
No
24
Short circuit:
Replace the indoor fan motor.
Short circuit:
Replace the vane motor and the indoor
electronic control P.C. board.
Is electricity
conducted? (The
on the
resistance is 0 Ω .)
The thermal fuse connected
to the terminal block has
failed.
Replace the terminal block
assembly.
Replace the indoor
power P.C. board, the
indoor terminal P.C.
No
board and the indoor fan
motor.
Replace the indoor fan motor.
Yes
Connect the connector CN10A or repair
disconnection.
Yes
Yes
No