BoilerFaultCodes.com
E01 High Lockout

Your boiler has tried to start but failed to light the flame, leaving you without 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: Failure to ignite

What causes this fault?

This fault occurs when the boiler's control system fails to detect a steady flame after several attempts to start. It is usually caused by a worn ignition spark that cannot light the gas, or a dirty sensor that fails to tell the boiler the flame is actually lit. In some cases, the gas valve may be stuck or electrical components have failed, preventing the combustion process from beginning.

This fault can appear more frequently during the first cold snap of autumn when internal components that have been idle all summer struggle to move or ignite correctly.

Typical repair cost £120-350 (including labour)

DIY fix possible

Check if other gas appliances in your home, such as a hob, are working correctly.Ensure your gas meter has credit and the isolation valve is open.Press and hold the 'Reset' button for two seconds to see if the boiler restarts.

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