Medium Warning
S.46 on Vaillant ecoTEC Pro 28

Your boiler has noticed an unstable flame when running at its lowest setting and is operating at a restricted level to prevent a complete breakdown.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Comfort protection: Minimum load, loss of flame. Comfort protection mode for flame loss at minimum load is activated.

What causes this fault?

This fault occurs when the boiler struggles to maintain a steady flame while running at its lowest power level. The most common cause is a dirty or worn-out sensing probe that can no longer accurately detect the fire, or an incorrect mix of gas and air preventing a consistent burn.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.28View →F.29View →S.41View →

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