How much does it cost to fix boiler error code 5 04?

Typical repair cost for the boiler 5 04 fault is £150-300 including labour.

5 04 High

Boiler Fault Code 5 04

Also written as 504 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code 5 04 appears across 1 boiler brand and 14 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is struggling to keep the flame lit correctly, causing it to detach from the burner, which prevents the unit from heating your home safely. (As reported on Ariston Clas HE R)

Pick your boiler brand for the 5 04 fix

Ariston 5 04 14 models

Source

Information for the 5 04 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 7 July 2026