SIE-86
Troubleshooting
Service Diagnosis
65
5.9
Power Supply Abnormalities or Faulty Indoor Printed Circuit Boards
(U4)
Remote Controller
Display
∗
or
UUU
U4444
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
(RF003)
Si-86.book Page 65 Friday, June 23, 2000 10:26 AM