How much does it cost to fix Heatline error code Lock-out?

Typical repair cost for the Heatline Lock-out fault is £90-180 including labour.

Lock-out High

Heatline Lock-out Fault Code

Q: What does the Heatline Lock-out fault code mean?

Your boiler has shut down to protect itself, likely because it got too hot or failed to light the gas flame.

Also written as LOCKOUT — same fault.

The Heatline Lock-out fault code means: your boiler has shut down to protect itself, likely because it got too hot or failed to light the gas flame.. It appears on 2 Heatline models in our database.

Technical description: Activated by overheat thermostat or ignition failure. Boiler has to be manually re-set by switching the control knob off (for 15 seconds) and on again.

Typical repair cost £90-180 (including labour)

DIY fix possible

Turn the main control knob to the 'Off' position.Wait for at least 15 seconds for the system to reset.Turn the control knob back to the 'On' or 'Winter' position and check if the flame ignites.

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Heatline models that show the Lock-out fault code

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

Source

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

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