Lennox LI012CI-160P432-1 Service Manual page 63

4. Malfunction of Zero-crossing Inspection Circuit Malfunction of the IDU Fan Motor U8
Main detection points:
● Instant energization afte de-energization while the capacitordischarges slowly?
● The zero-cross detectioncircuit of the mainboard is defined abnormal?
Malfunction diagnosis process:
Turn power off for
1minute,the turn
The zero-cross detection circuit
of the mainboard is defined
abnormal.Replace the mainboard
with the same model
60
Start
back on
U8 is still No
displayed
Yes
End
The unit returns to normal.
Conclusion:U8 is displayed due to
power off/on while the
capacitor discharges slowly.
Service Manual
Installation and Maintenance