Low
S.25 on Vaillant ecoTEC Pro

Your boiler is briefly keeping its internal parts running to safely cool down after you have finished using your hot water.

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.

What the manual says

Manufacturer manual

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

Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This status occurs because the internal components of your boiler become very hot while heating your shower or taps. The boiler needs to keep the pump and fan running for a short period to move that heat away and prevent the system from overheating. It is a normal part of the boiler's operation and ensures the longevity of the internal parts.

DIY fix possible

No action is required; this is a normal operating status and not a fault.Wait a few minutes for the boiler to complete the cooling cycle.Check that your hot water taps are fully closed.

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