12 High

Baxi 12 Fault Code

The Baxi 12 fault code means: your boiler has detected that the central heating system is not circulating or warming up as expected, meaning your radiators will not get hot.. It appears on 11 Baxi models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Central Heating Mode
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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Baxi models that show the 12 fault code

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

Source

Baxi 12 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026