Medium
C4 (ΔP-C) on Alpha Intec 50CS

Your boiler's internal pump is currently running at a fixed, constant speed rather than adjusting to the needs of your heating system.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Constant curve - H=4 m (Orange LED)

DIY fix possible

Check if the heating and hot water are still working as normal, as this is often an advisory status rather than a breakdown.Try resetting the boiler by turning the selector switch to 'RESET' for a few seconds.If the code persists and you have no heating, contact a professional to check the pump configuration.

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →