How much does it cost to fix Saunier Duval error code 42.?

Typical repair cost for the Saunier Duval 42. fault is £250-450 including labour.

42. High

Saunier Duval 42. Fault Code

Q: What does the Saunier Duval 42. fault code mean?

Your boiler's internal computer has encountered a critical error and can no longer safely manage the heating process, resulting in a system shutdown.

Also written as 42 — same fault.

The Saunier Duval 42. fault code means: your boiler's internal computer has encountered a critical error and can no longer safely manage the heating process, resulting in a system shutdown.. It appears on 2 Saunier Duval models in our database.

Technical description: There is an internal fault in the Automatic Control Module.

Typical repair cost £250-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Saunier Duval models that show the 42. fault code

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

Source

Saunier Duval 42. fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.

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