Troubleshooting by Error Code SiAF332111E
310 Part 6 Service Diagnosis
5.60 Transmission Error between Indoor Units and Outdoor
Units
Applicable
Models
All indoor unit models
All outdoor unit models
Error Code U4
Method of Error
Detection
Microcomputer checks if transmission between indoor and outdoor units is normal.
Error Decision
Conditions
Transmission is not carried out normally for a certain amount of time.
Supposed
Causes
Short circuit, wrong wiring, disconnection, or poor contact in indoor-outdoor transmission
wiring (F1/F2)
Outdoor unit power supply is OFF
System address does not match
Defective indoor unit PCB
Defective outdoor unit main PCB
Troubleshooting RXQ4/5AR
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
Caution
YES
NO
All indoor
unit remote
controllers of the same
refrigerant system
display
U4
.
Is indoor-outdoor
unit transmission
wiring normal?
Has the
indoor or
outdoor unit main
PCB been replaced, or
has the indoor-outdoor
unit transmission
wiring been
modified?
NO
YES
Replace the indoor unit PCB
indicated by the error code U4.
Fix the indoor-outdoor
unit transmission wiring.
NO
YES
Reset the power supply.
Press and hold the RESET
(BS5) button on the master
outdoor unit main PCB (A1P)
for 5 seconds.
∗ The unit will not operate for
up to 12 minutes.
A
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