Low Information
S.05 on Glow-worm Ultracom 2 CXI

Your boiler is temporarily cooling itself down after finishing a heating or hot water cycle, which is a normal part of its operation.

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 status occurs when the boiler has just finished heating your home or water and needs to dissipate excess heat from the internal heat exchanger. The internal pump and fan continue to run for a few minutes to circulate water and air, preventing the components from overheating or being damaged by 'heat soak'. This is a built-in safety feature rather than a mechanical failure.

DIY fix possible

Wait for 5 to 10 minutes for the boiler to complete its cooling cycleCheck that your radiator valves are open to allow heat to dissipateIf the code persists for hours, try resetting the boiler

Find a Gas Safe engineer
Search the official register →

Related fault codes

S.07View →S.08View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →