Error code reference

Lennox Hvac Error Code 104

There is a delay in the air-handler responding to the system.

First step from the service manual

Check all wiring connections. Cleared after unresponsive device responds to any inquiry.

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
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104 on my Lennox HVAC

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There is a delay in the air-handler responding

From Service Manual 832349, p.41:

1.Check all wiring connections. Cleared after unresponsive device responds to any inquiry.

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 104.

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