High Lockout
442 on Ideal Response SE

Your boiler's internal computer brain has developed a critical electronic fault and can no longer control the heating system safely.

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

Internal failure - electronic

What causes this fault?

This fault occurs when the boiler's main control board has suffered a terminal hardware failure and is no longer able to communicate with the rest of the system. The most common reason is age-related wear on the electronic components or a sudden electrical surge that has damaged the delicate circuitry.

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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