High Lockout
7F on Ideal Maximiser SE

Your boiler's internal computer has lost power or suffered a hardware failure, meaning it cannot control the heating or hot water functions.

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

Defective control panel or blown F3 fuse.

What causes this fault?

This fault occurs when the boiler's main control board loses electrical power or suffers an internal hardware failure. The most common reason is a blown fuse on the board caused by an electrical surge, though it can also happen if the circuit board itself has simply worn out and can no longer process commands.

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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