BoilerFaultCodes.com
A01 High Lockout

Your boiler has failed to light the flame, which means you currently have no heating or hot water.

Call an engineer soon

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

Technical description: No burner ignition – possible electrode error, defective gas valve or incorrect inlet gas pressure

What causes this fault?

This fault occurs when the boiler's control system attempts to light the burner but fails to detect a steady flame after several tries. The most common reasons include a worn-out ignition spark electrode that can no longer create a spark, or a gas valve that isn't opening correctly to allow fuel into the burner.

Typical repair cost £120-£350 (including labour)

DIY fix possible

Check if other gas appliances in your home, like a hob, are working to ensure gas is reaching the property.Verify that your gas prepaid meter has credit, if applicable.Press the 'Reset' button on the boiler control panel once to see if the system restarts.

Find a Gas Safe engineer

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