How much does it cost to fix boiler error code C4 (ΔP-C)?

Typical repair cost for the boiler C4 (ΔP-C) fault is £150-300 including labour.

C4 (ΔP-C) Medium

Boiler Fault Code C4 (ΔP-C)

Also written as C4PC — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code C4 (ΔP-C) appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's internal pump is currently running at a fixed, constant speed rather than adjusting to the needs of your heating system. (As reported on Alpha Intec 28GS)

Pick your boiler brand for the C4 (ΔP-C) fix

Alpha C4 (ΔP-C) 4 models

Source

Information for the C4 (ΔP-C) fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026