Mitsubishi Electric MSZ-LN18VG2W-E1 Service Manual page 38

D How to check miswiring and serial signal error
MUZ Type
The connection information to the Multi series is stored
in the indoor unit. Refer to "Deleting the memorized
abnormal condition" described in 10-2.1 to clear the error
history. When the error history is being cleared, the con-
nection information also will be initialized. The indoor unit
will be compatible with a low-standby-power model after
initialization.
OK
Is there rated voltage between outdoor terminal block S1 and S2?
Wait for 2 or more minutes after the power supply is turned on.
Touch S2 and S3 with tester probes and start the emergency operation.
When the emergency operation starts, does the rated voltage occur for 2
seconds between indoor terminal block S2 and S3?
Yes
Does the indoor POWER lamp
blink continuously 6 minutes after
the emergency operation starts?
Yes
Does the outdoor LED blink 6
times?
Yes
Does DC (6 V or more) occur
between indoor terminal block S2
and S3?
Yes
Turn the power supply OFF.
Replace the indoor power P.C.
board.
Turn the power supply ON.
Start the emergency operation.
Does the indoor POWER lamp
blink continuously 6 minutes after
the emergency operation starts?
Yes
Does DC (20 V or more) occur
between indoor terminal block S2
and S3?
Yes
Replace the indoor electronic
control P.C. board.
OBH766C
Turn OFF the power supply.
Is there rated voltage in the power supply?
Yes
Check for incorrect indoor-outdoor connecting wiring.
Was the indoor unit ever connected to
the Multi (MXZ) series and operated
Yes
(turned on)?
• Turn OFF inverter-controlled lighting equipment.
• Turn OFF the power supply and then turn ON again.
• Press EMERGENCY OPERATION switch.
Is serial signal error indicated 6 minutes later?
Yes
Turn the power supply ON.
Yes
No
Does the outdoor LED light up?
Confirm that the thermostat is OFF
and wiring is not loose.
No
Replace the outdoor inverter P.C. board.
No
Replace the outdoor inverter P.C. board.
Electric charge may remain immediately
*1
after the power supply is turned OFF.
Perform the procedure after 3 minutes.
No
Repair completed.
No
Replace the outdoor inverter P.C. board.*1
Check the power supply.
No
No
• Reinstall either the unit or the light away from each other.
• Attach a filter on remote control receiving section of the
No
indoor unit.
No
No
No
Yes
Wait for 2 or more minutes after the
power supply is turned ON. Touch
CN202
*1
and start the emergency operation.
During the emergency opera-
tion, does DC (2V or less) occur
*1
for 2 seconds between CN202
P.C. board?
38
Check for miswiring, broken wires, and loose wire
connection between the power supply and outdoor
terminal block S1 and between the power supply and
outdoor terminal block S2.
Turn the power supply OFF.
Turn the power supply ON.
and GND with tester probes
No
and GND on the indoor power
Yes
Replace the Replace the indoor
indoor power P.C. electronic control
board. P.C. board.