High Lockout
F.4 on Vaillant ecoMAX Pro 28E

Your boiler is failing to light the flame properly, which means it cannot heat your radiators or 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

Ignition fault.

What causes this fault?

This fault occurs when the boiler's control system attempts to start a flame but fails to detect one after several attempts. The most common reasons are a lack of gas reaching the burner, worn-out ignition sparks that can no longer bridge the gap, or a carbon-coated sensor that cannot 'see' the flame once it has lit.

This fault can be more frequent during the first cold snap of autumn when internal components that have sat idle all summer finally seize or fail under heavy use.

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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