Service Manual
Table Of Contents
SiUS281811E Troubleshooting by Error Codes
Part 6 Service Diagnosis 253
4.53 Transmission Error between Indoor and Outdoor Units in
the Same System
Error Code U9
Applicable
Models
All indoor units
All outdoor units
Method of Error
Detection
Error signal for the other indoor units is detected within the system by outdoor unit PCB.
Error Decision
Conditions
The error decision is made on any other indoor unit within the system concerned.
Supposed
Causes
Transmission error within or outside of other system
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
Caution
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
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.
Re-diagnose by display after
passage of 2 minutes or more.
Continue the operation.
NO
U9 has been
displayed for 2 minutes
or more.
NO
All the units are
indicating U9.
Turn ON all indoor units.
YES
YES