How much does it cost to fix boiler error code D.51?

Typical repair cost for the boiler D.51 fault is £90-180 including labour.

D.51 Medium

Boiler Fault Code D.51

Also written as D51 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code D.51 appears across 1 boiler brand and 25 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is signalling a setup issue related to the fan's speed range, meaning it is not operating at its intended maximum performance level. (As reported on Vaillant ecoTEC plus Regular)

Pick your boiler brand for the D.51 fix

Vaillant D.51 25 models

Source

Information for the D.51 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