Indoor Unit - Mitsubishi Electric MFZ-KJ25VE Service Manual

D How to check miswiring and serial signal error
MUFZ-KJ25/35
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 left lamp of the OPERA-
TION INDICATOR lamp on the indoor
unit blink continuously 6 minutes af-
ter the emergency operation starts?
Yes
Does the outdoor LED blink 6
times?
Yes
Does DC (6V or more) occur
between indoor terminal block S2
and S3?
Yes
Turn the power supply OFF.
Replace the indoor electronic
control P.C. board.
OBH666A
Turn OFF the power supply.
Is there rated voltage in the
power supply?
Yes
Turn ON the power supply.
Is there rated voltage between
outdoor terminal block S1 and S2?
Yes
Press EMERGENCY OPERATION switch once.
Does the left lamp of OPERATION INDICATOR
lamp on the indoor unit light up? <Confi rmation
of the power supply to the indoor unit>
Yes
Is the serial signal error
indicated 6 minutes later?
Yes
A
B Turn the power supply ON.
Yes
No
Does the outdoor LED light up?
Yes
Confi rm that the thermostat is OFF
and wiring is not loose.
No
Replace the outdoor inverter P.C. board. 1
No
Replace the outdoor inverter P.C. board. 1
Check the power supply.
No
Check the wiring.
No
No
Is there any miswiring, poor contact or wire dis-
connection of the indoor/outdoor connecting wire?
No
No
No
No
1.
Electric charge may remain immediately
after the power supply is turned OFF.
Perform the procedure after 3 minutes.
• Turn OFF inverter-controlled lighting equipment.
• Turn OFF the power supply and then turn it ON again.
• Press EMERGENCY OPERATION switch.
Is serial signal
error indicated 6
minutes later?
27
Yes
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 elec-
tronic control P.C. board.
A
• Reinstall either the unit or the light
away from each other.
• Attach a fi lter on remote control
No
receiving section of the indoor unit.
Yes
B
Correct the wiring.