Your boiler has not been fully configured for operation or there is a communication problem between the internal controls and the burner assembly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Installation in unfinished state - Fault in burner / Ignition valve
What causes this fault?
This fault occurs when the boiler's internal computer cannot successfully communicate with the burner system or hasn't been properly programmed to start. It is often caused by a loose connection, a faulty ignition lead, or a breakdown in the electronic control board that manages the gas flow. Effectively, the boiler has safety-locked because it cannot verify that it is safe to ignite the flame.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like b4 — no call-out fees, no surprises.
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Viessmann Vitodens Tec is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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