Mitsubishi Electric MUZ-EF25VG Service Manual page 46

M How to check miswiring and serial signal error
Check for incorrect indoor-outdoor connecting wiring.
Yes
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
• Turn OFF inverter-controlled lighting equipment.
• Turn OFF the power supply and then turn ON again.
• Press EMERGENCY OPERATION switch.
Is there rated voltage between outdoor terminal block S1 and S2?
Wait for 2 or more minutes after the main 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 upper lamp of OPERA-
TION INDICATOR lamp on the
indoor unit blink continuously 6 min-
utes after the emergency operation
starts?
Yes
Does the outdoor LED blink 6
times?
Yes
Does DC (6V or more) occur be-
tween indoor terminal block S2 and
S3?
Yes
Replace the indoor electronic
control P.C. board. 1
OBH832
Turn the main 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
(turned on)?
Is serial signal
error indicated 6
No
minutes later?
Yes
Turn the main power supply ON.
Yes
Does the outdoor LED light up?
No
Confi rm that the thermostat is OFF
and wiring is not loose.
Replace the outdoor inverter P.C. board. 1
No
Replace the outdoor inverter P.C. board. 1
No
1.
Electric charge may remain immediately
after the main power supply is turned OFF.
Wait 3 minutes before indoor electronic
control P.C. board replacement.
No
No
No
No
No
Yes
46
Check the power supply.
• Reinstall either the unit or the light
away from each other.
• Attach a fi lter on remote control
receiving section of the indoor unit.
Check for miswiring, broken wires, and loose
wire connection between the main power
supply and outdoor terminal block S1 and
between the main power supply and outdoor
terminal block S2.
Replace the indoor elec-
tronic control P.C. board.