Error code reference
Lennox Air Conditioner Error Code E431
PFC detected an over-current condition of 100A (inverter code 27), indicating power interruption, brownout…
PFC detected an over-current condition of 100A (inverter code 27), indicating power interruption, brownout, poor electrical connection or loose inverter input wire.
First step from the service manual
Check for proper main power to outdoor unit and for any loose electrical connections.
The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.
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- Step-by-step tests with expected resistance, voltage, and continuity values
- Wiring diagram references and connector pinouts from the OEM service manual
- Verified part numbers when replacement is required
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