High Lockout
F004 on Intergas Xtreme 24

Your boiler is trying to ignite but cannot establish a flame, meaning you have no heating or hot water.

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

No flame during start-up.

What causes this fault?

This fault occurs when the boiler's control system attempts to start a flame but fails to detect one within a safe timeframe. The most common reasons include a lack of gas supply to the unit, a worn-out ignition spark plug, or a component failure that prevents the gas valve from opening correctly.

This fault is more frequent during extreme cold snaps, as external gas meters or pipes can sometimes freeze, restricting the pressure required for the boiler to ignite.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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