High Lockout
A09-12 on Potterton Powermax HE

Your boiler's main internal computer has developed a serious communication fault and can no longer control the heating process 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 boiler control failure

What causes this fault?

This fault occurs when the boiler's central control board suffers an internal electronic failure, meaning it can no longer send or receive signals from the sensors and gas valve. It is typically caused by aged electrical components on the circuit board wearing out or developing a short circuit over time. In some cases, a loose or damaged wiring connection between the board and the main internal components can also trigger this communication breakdown.

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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