S.14 Low

Vaillant S.14 Fault Code

Also written as S14 — same fault.

The Vaillant S.14 fault code means: your boiler is operating normally and is currently in the process of starting up the burner to provide heat or hot water.. It appears on 26 Vaillant models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Burner ignited

What causes the Vaillant S.14 fault?

This is not actually a fault, but rather a status message indicating that the boiler has successfully lit the flame. It physically occurs when the gas valve opens and the spark electrode ignites the burner to begin a heating or hot water cycle. You are seeing this because the boiler is functioning exactly as it should during its normal startup sequence.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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Vaillant models that show the S.14 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant S.14 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026