Service Manual

SiUS041638E Troubleshooting
Service Diagnosis 68
4.8 Signal Transmission Error on Outdoor Unit PCB
Error Code
U7
Method of Error
Detection
Communication error between microcomputer mounted on the main microcomputer and PM1.
Error Decision
Conditions

The abnormality is determined when the data sent from the PM1 can not be received for 9
seconds.

The error counter is reset when the data from the PM1 can be successfully received.
Supposed
Causes

Defective outdoor unit PCB
Troubleshooting
(R21808)
Caution
YES
NO
Turn off the power. Then, turn on
the power to restart the system.
Error again?
The cause can be an
external factor other than
the malfunction.
Observe the operating
condition in long term.
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
Replace the outdoor unit
PCB (main PCB).