Panasonic WH-SXC09H3E8 Service Manual page 184

16.5.20 PCB Communication Error (H74)
Malfunction Decision Conditions:
When External PCB connection is select "YES" and no communication with External PCB micon for 10 seconds
and above.
Malfunction Caused:
1 Faulty connector connection.
2 Faulty indoor PCB.
3 Faulty indoor sub PCB.
Abnormality Judgment:
After 1 minute operation started.
PCB communication error
H74 happens check connection at CN-PWR normal?
Check CN-PWR 230/240 V?
Check CN-COMM situation on terminal 1 & 2 and 3 & 1
Replace indoor PCB
YES
YES
YES
184
For safety reason and to prevent
component breakdown, always switch
Caution
off the power before remove and
connect the component.
NO
● Correct connection at CN-PWR
NO
● Abnormal AC POWER supply
NO
● Replace sub PCB