Lennox LI036CI-180P432 Service Manual page 62

Service Manual
5. 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:
The zero-cross detection circuit
of the mainboard is defined
abnormal.Replace the mainboard
Installation and Maintenance
Start
Turn power off for
1minute,the turn
back on
U8 is still No
displayed
Yes
with the same model
End
The unit returns to normal.
Conclusion:U8 is displayed due to
power off/on while the
capacitor discharges slowly.
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