How much does it cost to fix Chaffoteaux error code 8.4.2?

Typical repair cost for the Chaffoteaux 8.4.2 fault is £120-280 including labour.

8.4.2 High

Chaffoteaux 8.4.2 Fault Code

Q: What does the Chaffoteaux 8.4.2 fault code mean?

Your boiler is starting to heat water but quickly shuts down the flame, meaning you will likely have cold or flickering water temperatures.

Also written as 842 — same fault.

The Chaffoteaux 8.4.2 fault code means: your boiler is starting to heat water but quickly shuts down the flame, meaning you will likely have cold or flickering water temperatures.. It appears on 3 Chaffoteaux models in our database.

Technical description: Burner goes out on hot water demand

Typical repair cost £120-280 (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 8.4.2 fault code

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

Source

Chaffoteaux 8.4.2 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