Error code reference

Trane Furnace Error Code 12

Ignitor relay failure internal in board

Ignitor relay failure internal in board. Replace IFC.

First step from the service manual

Replace IFC (Integrated Furnace Control).

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
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12 on my Trane Furnace

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Ignitor relay failure internal in board

From Service Manual 203847, p.19:

1.Replace IFC (Integrated Furnace Control).

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 12.

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