BoilerFaultCodes.com
5x High Lockout

Your boiler's central computer has encountered an internal error and can no longer control the heating or hot water safely.

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: problem with the main board exists

What causes this fault?

This fault occurs when the boiler’s main control board suffers a critical electronic failure or loses communication with its internal sensors. It is usually caused by age-related degradation of the circuit components or a sudden electrical surge that damages the board's memory. Because the 'brain' can no longer guarantee the boiler is operating safely, it shuts the entire system down as a precaution.

While this can happen at any time, it is slightly more common during stormy weather when power surges or lightning strikes can cause electrical damage to the sensitive circuit board.

Typical repair cost £250-£450 (including labour)

Engineer required

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

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