SiBE121135_A Troubleshooting for RA Indoor Unit
Service Diagnosis 182
5.7 Signal Transmission Error (between Indoor Unit and
Outdoor Unit)
Error Code U4
Method of Error
Detection
The data received from the outdoor unit in signal transmission is checked whether it is normal.
Error Decision
Conditions
The data sent from the outdoor unit cannot be received normally, or the content of the data is
abnormal.
Supposed
Causes
îš„ Wiring error
îš„ Breaking of the connection wires between the indoor and outdoor units (wire No. 3)
îš„ Defective outdoor unit PCB
îš„ Short circuit inside the fan motor winding
îš„ Defective indoor unit PCB
îš„ Disturbed power supply waveform
Troubleshooting
Check No.11
Refer to P.233
Check the voltage of the indoor
unit-outdoor unit connection wires
between No. 1 and No. 3, and
between No. 2 and No. 3.
Check No.11
Check the power supply
waveform.
YES
YES
Replace the indoor unit PCB.
Locate the cause of the
disturbance of the power
supply waveform, and correct
it.
NO
(R18383)
NO
YES
YES
NO
NO
Caution
Correct the indoor unit -
outdoor unit connection wires.
Diagnose the outdoor unit
PCB.
Replace the connection wires
between the indoor unit and
the outdoor unit.
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
Check the indoor unit - outdoor
unit connection wires.
Is there any wiring error?
Properly insulated?
Check the LED A on the outdoor
unit PCB.
Is LED A blinking?
Is there any disturbance?
YES
NO
Replace both the fan motor
and the outdoor unit PCB.
Rotate the
outdoor fan by hand.
Does the outdoor fan rotate
smoothly?
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