Low Information
S.25 on Vaillant ecoTEC plus Regular

Your boiler is busy prepping for a heating cycle by checking its internal sensors and clearing the flue, but if it stays stuck on this display, it may be failing to light.

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

Fan and water pump running

What causes this fault?

This code appears when the boiler begins its startup sequence, spinning up the fan and water pump to ensure the system is safe to ignite. If the boiler becomes stuck on this screen, it usually means the internal controls are waiting for a signal to proceed that isn't arriving. In many cases, this is caused by a minor electrical communication issue or a component failing to reach the necessary speed to trigger the next step.

DIY fix possible

Wait 5-10 minutes to see if the boiler progresses to a fire-up sequenceEnsure your thermostat is calling for heat (turned up)Reset the boiler using the button with the flame/cross icon

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