High Lockout
Condition K on Worcester Bosch 24CDi BF

Your boiler's internal computer brain is failing to communicate correctly, often due to moisture or a significant electronic fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Light indication during fault not covered by other details. Control board is likely to be wet, damaged, or malfunctioning.

What causes this fault?

This fault occurs when the boiler's main control board suffers a critical internal failure or a loss of signal between components. The most common reason is moisture ingress from a small internal leak or dampness in the air reaching the electronics and short-circuiting the board. In some cases, it can also be triggered by a loose or damaged wiring harness that prevents the boiler's 'brain' from sending instructions to the rest of the unit.

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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