High Lockout
26 on Ideal Maximiser SE

Your boiler has shut down because the mixture of gas and air required for a safe flame is incorrect, often due to a blockage or a dirty internal component.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Improper gas/air ratio. Check the air restriction and the gas injector for the correct diameter, mounting, and pollution.

What causes this fault?

This fault happens because the boiler cannot achieve the precise balance of gas and oxygen needed for safe combustion. It is typically caused by a buildup of dust or debris in the air intake or a blockage in the internal nozzle that delivers gas to the burner. When the sensors detect that the mixture is unstable or inefficient, the boiler shuts down as a safety precaution.

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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