Low Information
S.25 on Glow-worm Ultracom 35 Store

Your boiler is staying in a cooling-down mode because it thinks the internal temperature is still too high after the heating or hot water has turned off.

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

pump / fan overrun

What causes this fault?

This occurs when the boiler keeps its internal pump or fan running after a heating cycle to safely dissipate leftover heat. It is usually a normal safety function, but if it persists, it may indicate that the water is struggling to move through the system due to a blockage or a pump that is beginning to fail. In some cases, a faulty internal sensor might also be tricking the boiler into thinking it is hotter than it actually is.

DIY fix possible

Check that all radiator valves are not fully closedEnsure the boiler pressure is between 1.0 and 1.5 barWait for 5-10 minutes to see if the status clears automatically once the unit cools

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Related fault codes

S.20View →S.24View →

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