Medium Warning
S.46 on Vaillant ecoTEC Pro 24

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.

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.

DIY fix possible

Check that the gas supply is active and credit is on the meterPress the 'Reset' button (flame symbol) to clear the statusMonitor the boiler to see if the code returns or leads to an F.28 or F.29 faultContact a Gas Safe engineer if the problem persists for a full service and ionisation check

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