Mitsubishi Electric MUZ-AY25VG Service Manual page 54

M How to check miswiring and serial signal error
Check for incorrect indoor-outdoor connecting wiring.
The connection information to the Multi series is stored
in the indoor unit. Refer to "Deleting the memorized
abnormal condition" described in 12-2.1 to clear the
error history. When the error history is being cleared,
the connection 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 multimeter 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 Upper lamp of OPERATION
INDICATOR lamp blink continuously 6 min-
utes 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
Replace the indoor electronic
control P.C. board.
OBH931
Turn the power supply OFF.
Is there rated voltage in the power supply?
Yes
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 the emergency operation switch.
Is serial signal error indicated 6 minutes later?
Yes
Turn the power supply ON.
Yes
No
No
No
Check the power supply.
No
No
No
No
No
Does the outdoor LED light up?
Yes
Confirm that the thermostat is OFF
and wiring is not loose.
Replace the outdoor inverter P.C. board. *1
Replace the outdoor inverter P.C. board. *1
*1 Electric charge may remain immediately
after the power supply is turned OFF.
Perform the procedure after 3 minutes.
54
• Reinstall either the unit or the light away from
each other.
• Attach a filter on remote control receiving sec-
tion of the indoor unit.
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.
Replace the indoor
electronic control
No
P.C. board.