Overheat thermostat lockout High

Ideal Overheat thermostat lockout Fault Code

Also written as OVERHEATTHERMOSTATLOCKOUT — same fault.

The Ideal Overheat thermostat lockout fault code means: your boiler has detected that it is getting too hot and has automatically switched itself off to prevent damage or danger.. It appears on 8 Ideal 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: The boiler is fitted with a safety 'cutout' thermostat. This thermostat will extinguish the pilot and shut down the boiler in the event of overheating.
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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Ideal models that show the Overheat thermostat lockout fault code

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

Source

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

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