Trouble shooting Si04-11572 Service Diagnosis5.7 Power Supply Abnormalities or Faulty Indoor PrintedCircuit BoardsRemoteControllerDisplay∗ or U4U4U4U4Indoor unit LEDDisplayMethod ofMalfunctionDetection1. The proper program operation of the microcomputer is checked by the program.2. In indoor-outdoor signal communications, the indoor unit determines whether the outdoorunit receives signals properly by detecting signals transmitted by the outdoor unit to theindoor unit.MalfunctionDecisionConditions1. When the microcomputer program does not function properly.2. When the indoor unit determines that the indoor unit does not properly receive signalstransmitted by the outdoor unit in indoor-outdoor signal communications.SupposedCauses" 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).TroubleshootingCheck the varistor of the indoorunit PCB.Check voltage of AC power supply.220 ~ 240V ±10%YESYESCheck the power supply, andcorrect it if not proper.Replace the varistor.Replace the fuse.Replace indoor PCB (1).Does thepower supply have the ratedvoltage?NOIs it damaged?NOCheck the fuse of the indoor unitPCB.YESIs there conductivity? NO(R1949)CautionBe sure to turn off power switch before connect or disconnect connector,or parts damage may be occurred.
