Low Information
S.15 on Vaillant ecoTEC Pro 24

Your boiler is simply taking a moment to cool itself down after heating your water, which is a normal part of its operation.

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

DHW mode: Pump/fan overrun. The pump/fan overrun for domestic hot water mode is activated.

What causes this fault?

This occurs because the boiler has just finished heating your taps or shower and needs to move heat away from the internal components. The pump and fan continue to run briefly to dissipate this residual heat and protect the system from overheating. It is a standard safety feature rather than a mechanical failure.

DIY fix possible

Wait for a few minutes as this is a status code, not a permanent faultCheck that your hot water taps are fully turned offEnsure your radiator valves are open to allow heat to dissipate if the boiler requires it

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