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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
YES
YES
YES
NO
When abnormality indication starts again
Measure the AC voltage at terminal 1 & 2 of outdoor unit
terminal board
Is the measured voltage 230/240V?
● AC power supply abnormal fluctuation
● Defect in communication circuitry
of outdoor unit PCB
● Replace the PCB
● Improper connection at terminals
indoor/outdoor
● Check indoor/outdoor connecting cable
Measure the DC voltage at terminal 2 & 3 (communication
terminals) of outdoor unit terminal board
Is the measured DC voltage fluctuate between 10~70V?
● Improper connection at terminals
indoor/outdoor
● Check indoor/outdoor connecting cable
Measure the AC voltage at terminal 1 & 2 of indoor unit
terminal board
Is the measured voltage 230/240V?
● Defect in receiver/transmitter module of
the communication circuitry in indoor
unit PCB
● Replace the indoor unit PCB
YES
Measure the DC voltage at terminal 2 & 3 of indoor unit
terminal board
Is the measured DC voltage fluctuate between 18~25V?
For safety reason and to prevent
component breakdown, always switch
off the power before remove and
connect the component.
NO
NO
NO
Caution
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