How much does it cost to fix Chaffoteaux error code 40 50 70?

Typical repair cost for the Chaffoteaux 40 50 70 fault is £120-250 including labour.

40 50 70 High

Chaffoteaux 40 50 70 Fault Code

Q: What does the Chaffoteaux 40 50 70 fault code mean?

Your boiler is struggling to accurately detect the temperature of the water being sent to your hot water tank, causing the system to stop heating it properly.

Also written as 405070 — same fault.

The Chaffoteaux 40 50 70 fault code means: your boiler is struggling to accurately detect the temperature of the water being sent to your hot water tank, causing the system to stop heating it properly.. It appears on 2 Chaffoteaux models in our database.

Technical description: Thermistor cylinder bypassed

Typical repair cost £120-250 (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 40 50 70 fault code

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

Source

Chaffoteaux 40 50 70 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