High Lockout
F.28 on Vaillant ecoTEC Pro / ecoTEC Plus

Your boiler has failed to ignite and has locked itself out for safety, meaning you currently 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

Failure during start up – ignition unsuccessful to start

What causes this fault?

This fault occurs when the boiler tries to light the flame but fails to detect one after several attempts. The most common reasons are a lack of gas reaching the unit, worn-out spark components that can't create a flame, or a faulty internal valve that isn't releasing fuel correctly.

This fault is more common during extreme cold spells, as external gas meters or pipes can freeze and restrict the flow of fuel to the appliance.

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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