Error code reference

Lennox Heat Pump Error Code Green ON / Red ON

Circuit board failure

Circuit board failure — internal component failure on defrost control board.

First step from the service manual

Cycle 24 volt power to board. If code does not clear, 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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Green ON / Red ON on my Lennox Heat Pump

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Circuit board failure — internal component

From Service Manual 524091, p.23:

1.Cycle 24 volt power to board. If code does not clear, replace board.

2.Measure line voltage at the power cord terminal block. Expected: 120 VAC (L1 to neutral) or 208 to 240 VAC between L1 and L2 under load.

3.Inspect the cord strain relief and terminal block screws for signs of arcing or heat discoloration. Loose connections here mimic an intermittent power failure to the control board.

Part W10911048

Power cord assembly

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First step from the service manual

Get the full diagnostic procedure for Green ON / Red ON.

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