Trouble shooting
Si04-115
72
Service Diagnosis
5.7
Power Supply Abnormalities or Faulty Indoor Printed
Circuit Boards
Remote
Controller
Display
∗
or
U4
U4
U4
U4
Indoor unit LED
Display
Method of
Malfunction
Detection
1. The proper program operation of the microcomputer is checked by the program.
2. In indoor-outdoor signal communications, the indoor unit determines whether the outdoor
unit receives signals properly by detecting signals transmitted by the outdoor unit to the
indoor unit.
Malfunction
Decision
Conditions
1. When the microcomputer program does not function properly.
2. When the indoor unit determines that the indoor unit does not properly receive signals
transmitted by the outdoor unit in indoor-outdoor signal communications.
Supposed
Causes
"
Display disabled by fault power supply.
"
Faulty signal transmitting/receiving circuit in indoor printed circuit boards (1) and (2)
"
Microcomputer program is in abnormal condition due to an external factor.
• Noise.
• Momentary voltage drop.
• Momentary power failure, etc.
"
Faulty indoor unit PCBs (1) and (2).
Troubleshooting
Check the varistor of the indoor
unit PCB.
Check voltage of AC power supply.
220 ~ 240V ±10%
YES
YES
Check the power supply, and
correct it if not proper.
Replace the varistor.
Replace the fuse.
Replace indoor PCB (1).
Does the
power supply have the rated
voltage?
NO
Is it damaged?
NO
Check the fuse of the indoor unit
PCB.
YES
Is there conductivity?
NO
(R1949)
Caution
Be sure to turn off power switch before connect or disconnect connector,
or parts damage may be occurred.
