Troubleshooting by Error Codes
4.53 Transmission Error between Indoor and Outdoor Units in
the Same System
U9
Error Code
Applicable
All indoor units
Models
All outdoor units
Method of Error
Error signal for the other indoor units is detected within the system by outdoor unit PCB.
Detection
Error Decision
The error decision is made on any other indoor unit within the system concerned.
Conditions
Supposed
Transmission error within or outside of other system
Causes
Defective electronic expansion valve in indoor unit of other system
Defective PCB of indoor unit in other system
Improper connection of transmission wiring between indoor and outdoor unit
Troubleshooting
284
Be sure to turn off the power switch before connecting or disconnecting
Caution
connectors, or parts may be damaged.
Turn ON all indoor units.
NO
All the units are
indicating U9.
YES
U9 has been
NO
displayed for 2 minutes
or more.
YES
SiUS281811EA
Continue the operation.
Re-diagnose by display after
passage of 2 minutes or more.
The indoor unit PCB indicated by
the error code U9 is normal.
Check for the indoor unit of other
system, and then conduct
troubleshooting by diagnosis
according to the Error Code
Flowchart.
Part 6 Service Diagnosis