How much does it cost to fix Chaffoteaux error code 9.ii?

Typical repair cost for the Chaffoteaux 9.ii fault is £150-350 including labour.

9.ii High

Chaffoteaux 9.ii Fault Code

Q: What does the Chaffoteaux 9.ii fault code mean?

Your boiler is overheating because water is not flowing through it properly, which has caused it to automatically shut down as a safety precaution.

Also written as 9II — same fault.

The Chaffoteaux 9.ii fault code means: your boiler is overheating because water is not flowing through it properly, which has caused it to automatically shut down as a safety precaution.. It appears on 3 Chaffoteaux models in our database.

Technical description: Excessive temperature rise across boiler - Low water flow rate (Pump defective/High resistance)

Typical repair cost £150-350 (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 9.ii fault code

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

Source

Chaffoteaux 9.ii 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