High Lockout
F.28 on Vaillant ecoTEC Plus 65

Your boiler is trying to light itself to provide heat, but it is failing to create a flame, likely because it is not getting enough gas or the spark isn't catching.

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

The burner fails to ignite after five attempts, the device does not start up and switches to “Fault”.

What causes this fault?

This fault occurs when your boiler attempts to fire up but cannot detect a stable flame after several attempts. The most common reasons are a lack of gas reaching the unit, a worn-out spark plug that cannot ignite the fuel, or a internal sensor that is too dirty to 'see' the flame correctly.

In freezing temperatures, this code can be triggered if your external gas meter regulator or condensate pipe freezes, physically blocking the boiler's ability to operate.

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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