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S.25 on Vaillant ecoTEC sustain

Your boiler is briefly cooling itself down after providing hot water and will resume normal operation in a few moments.

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 status occurs because your boiler needs to dissipate excess heat after you finish using hot water. The pump and fan continue to run for a short period to move heat away from the internal components and prevent any damage from overheating. Once the internal temperature has dropped to a safe level, the boiler will automatically return to its normal standby mode.

DIY fix possible

Wait 5-10 minutes for the boiler to complete its cooling cycleCheck that your radiator valves are open to allow heat to dissipateEnsure your system pressure is between 1.0 and 1.5 bar

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Related fault codes

S.07View →S.20View →S.24View →

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