High Lockout
4P on Ideal Maximiser SE

Your boiler has lost its connection to an internal safety sensor and has shut down as a precaution to prevent damage.

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

Safety sensor not connected.

What causes this fault?

This fault occurs when the boiler's main control board loses communication with the internal safety sensor that monitors for overheating. The most common reason is a loose or corroded electrical connection, but it can also be caused by the sensor itself failing or a fault within the main circuit board.

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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