Error code reference
Lennox Heat Pump Error Code OFF/OFF
No power (24V) to board terminals R & C or board failure.
No power (24V) to board terminals R & C or board failure.
First step from the service manual
Check control transformer power (24V). If power is available to board and LEDs do not light, replace board.
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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