Error code reference

Lennox Hvac Error Code 351

There is a problem with the air-handler's first stage electric heat (pilot relay contacts did not close or…

There is a problem with the air-handler's first stage electric heat (pilot relay contacts did not close or relay coil did not energize).

First step from the service manual

Check relay coil and contacts. The alarm clears after stage 1 relay is detected.

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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351 on my Lennox HVAC

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There is a problem with the air-handler's first

From Service Manual 830275, p.47:

1.Check relay coil and contacts. The alarm clears after stage 1 relay is detected.

2.Measure control board supply voltage at the test points. Expected: 12 VDC and 5 VDC; a drop below 4.75 VDC on the logic rail points to a failed onboard regulator.

3.Inspect all connectors on the main control for corrosion, thermal stress, or backed-out pins. Reseat each connector with the power disconnected.

Part WPW10804018

Electronic control board

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First step from the service manual

Get the full diagnostic procedure for 351.

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