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

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

C4 (ΔP-C) Medium

Alpha C4 (ΔP-C) Fault Code

Q: What does the Alpha C4 (ΔP-C) fault code mean?

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

Also written as C4PC — same fault.

The Alpha C4 (ΔP-C) fault code means: your boiler's internal pump is currently running at a fixed, constant speed rather than adjusting to the needs of your heating system.. It appears on 4 Alpha models in our database.

Technical description: Constant curve - H=4 m (Orange LED)

Typical repair cost £150-300 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Alpha models that show the C4 (ΔP-C) fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Alpha C4 (ΔP-C) fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.

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