Panasonic CS-E18SD3UAW service manual - Page 72

15.5 Self-diagnosis Method 15.5.1 H11 (Indoor/Outdoor Abnormal Communication) Malfunction Decision Conditions  During startup and operation of cooling and heating, the data received from outdoor unit in indoor unit signal transmission is checked whether it is normal. Malfunction Caused  Faulty indoor unit PCB.  Faulty outdoor unit PCB.  Indoor unit-outdoor unit signal transmission error due to wiring error.  Indoor unit-outdoor unit signal transmission error due to breaking of wire in the connection wires between the indoor and outdoor units. Troubleshooting When abnormality indication starts again Measure the AC voltage at terminal 1 & 2 of outdoor unit terminal board Caution For safety reason and to prevent component breakdown, always switch off the power before remove and connect the component. Is the measured voltage 230/240V? YES Measure the DC voltage at terminal 2 & 3 (communication terminals) of outdoor unit terminal board NO AC power supply abnormal fluctuation Is the measured DC voltage fluctuate between 10~70V? YES Measure the AC voltage at terminal 1 & 2 of indoor unit terminal board NO Defect in communication circuitry of outdoor unit PCB Replace the PCB Is the measured voltage 230/240V? YES Measure the DC voltage at terminal 2 & 3 of indoor unit terminal board NO Improper connection at terminals indoor/outdoor Check indoor/outdoor connecting cable Is the measured DC voltage fluctuate between 10~70V? NO Improper connection at terminals indoor/outdoor Check indoor/outdoor connecting cable YES Defect in receiver/transmitter module of the communication circuitry in indoor unit PCB Replace the indoor unit PCB 72