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

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

UNSTABLE FLAMES Emergency

Chaffoteaux UNSTABLE FLAMES Fault Code

Q: What does the Chaffoteaux UNSTABLE FLAMES fault code mean?

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.

Also written as UNSTABLEFLAMES — same fault.

The Chaffoteaux UNSTABLE FLAMES fault code means: 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.. It appears on 5 Chaffoteaux models in our database.

Technical description: I) Water in gas line; II) Faulty flue

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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Chaffoteaux models that show the UNSTABLE FLAMES fault code

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

Source

Chaffoteaux UNSTABLE FLAMES fault code information on this page is sourced and cross-checked against the official Chaffoteaux service / installation manuals for each affected model.

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