Transmission Error Between Indoor Units And Outdoor Units - Daikin SkyAir RZR-TA Series Service Manual

Troubleshooting by Error Codes
4.50 Transmission Error between Indoor Units and Outdoor
Units
U4
Error Code
Applicable All indoor and outdoor units
Models
Method of Error Microcomputer checks if transmission between indoor and outdoor units is normal.
Detection
Error Decision When transmission is not carried out normally for a certain amount of time
Conditions
Supposed
 Indoor to outdoor transmission wiring F1, F2 disconnection, short circuit or wrong wiring
Causes  Outdoor unit power supply is OFF
 System address does not match
 Defective indoor unit PCB
 Defective outdoor main PCB
Troubleshooting
280
Be sure to turn off the power switch before connecting or disconnecting
Caution connectors, or parts may be damaged.
Has the
indoor or outdoor
unit PCB been
YES
replaced, or has the
indoor-outdoor unit
transmission wiring
been modified?
NO
All indoor
unit remote controllers
NO
of the same refrigerant system
display U4 .
YES
Reset the power supply.
A Go to the next page.
Are the
YES
indoor-outdoor unit
transmission wirings
normal?
NO
SiUS281811EA
Press and hold the RESET
(BS5) button on the master
outdoor unit PCB for 5 seconds.
∗ The unit will not operate for
up to 12 minutes.
Replace the indoor unit PCB
indicated by the error code
U4.
Fix the indoor-outdoor
unit transmission wiring.
Part 6 Service Diagnosis