Low Information
S.4 on Vaillant ecoTEC Plus 635

Your boiler is operating normally and is currently in the process of starting up the burner to provide heat or hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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 this fault?

This is not a fault, but rather a status message indicating that the boiler has successfully lit the flame. It confirms that the internal ignition sequence is complete and the unit is now producing heat for your radiators or hot water. You will see this code every time the boiler starts up as part of its normal, healthy operation.

DIY fix possible

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

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Related fault codes

S.0View →S.1View →S.3View →S.7View →S.8View →

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