How much does it cost to fix Halstead error code 12?

Typical repair cost for the Halstead 12 fault is £120-£220 including labour.

12 High

Halstead 12 Fault Code

Q: What does the Halstead 12 fault code mean?

Your boiler has stopped working because it cannot properly detect the temperature of the water flowing through your heating system, so it is choosing not to light for safety reasons.

The Halstead 12 fault code means: your boiler has stopped working because it cannot properly detect the temperature of the water flowing through your heating system, so it is choosing not to light for safety reasons.. It appears on 8 Halstead models in our database.

Technical description: No ignition - CH Flow thermistor failure

Typical repair cost £120-£220 (including labour)

Engineer required

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

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Halstead models that show the 12 fault code

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

Source

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

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