Overheat thermostat activated High

Halstead Overheat thermostat activated Fault Code

Q: What does the Halstead Overheat thermostat activated fault code mean?

Your boiler has switched itself off because it has become dangerously hot, likely due to a circulation problem or a faulty safety sensor.

Q: How much does it cost to fix Halstead error code Overheat thermostat activated?

Typical repair cost for the Halstead Overheat thermostat activated fault is £150-300 including labour.

Also written as OVERHEATTHERMOSTATACTIVATED — same fault.

The Halstead Overheat thermostat activated fault code means: your boiler has switched itself off because it has become dangerously hot, likely due to a circulation problem or a faulty safety sensor.. It appears on 4 Halstead models in our database.

Technical description: Boiler temperature > 105°C • Check CH/O’heat thermistor • Check wires to sensor • Check no air is in CH system • Check PCB • Check pump

Typical repair cost £150-300 (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 Overheat thermostat activated fault code

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

Source

Halstead Overheat thermostat activated 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