High
F12 on Vaillant ecoMAX Pro 18E

Your boiler's electronic control panel has lost communication with the main computer inside the unit, meaning the boiler has stopped working because it cannot receive instructions.

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

No reception by the local user interface

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

F11View →F13View →

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