High Lockout
F18 on Saunier Duval Isotwin F30E

Your boiler's control panel and the internal computer are having trouble communicating with each other, meaning the display may not work or respond to your commands.

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

User interface fault. Faulty user interface

What causes this fault?

This fault occurs when the data link between the display panel you interact with and the main computer inside the boiler is broken. The most common reason is an electronic component failure on one of the circuit boards or a loose connection in the internal wiring harness.

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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Related fault codes

F13View →

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