How much does it cost to fix boiler error code UNSTABLE FLAMES?

Typical repair cost for the boiler UNSTABLE FLAMES fault is £150-300 including labour.

UNSTABLE FLAMES Emergency

Boiler Fault Code UNSTABLE FLAMES

Also written as UNSTABLEFLAMES — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code UNSTABLE FLAMES appears across 1 boiler brand and 5 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 a steady flame, which suggests either moisture is trapped in the gas supply or the system cannot breathe properly through its exhaust. (As reported on Chaffoteaux Britony Duo 55)

Pick your boiler brand for the UNSTABLE FLAMES fix

Chaffoteaux UNSTABLE FLAMES 5 models

Source

Information for the UNSTABLE FLAMES 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