What does the Chaffoteaux UNSTABLE FLAMES fault code mean?

Your boiler is struggling to keep the fire lit safely, which could prevent your heating or hot water from working consistently.

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

Typical repair cost for the Chaffoteaux UNSTABLE FLAMES fault is £120-250 including labour.

i) Water in gas line ii) Inlet pressure too high for governor iii) Faulty flue

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Almost always a stuck diverter valve on combis.

Older boilers — thermocouple, draught, gas supply.

Safety-critical — turn off, read this.