BoilerFaultCodes.com
b4 High Lockout

Your boiler has not been fully configured for operation or there is a communication problem between the internal controls and the burner assembly.

Call an engineer soon

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.

Typical repair cost £120-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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