High Lockout
F11 on Vaillant ecoMAX Pro 28E

Your boiler's main internal computer is having trouble communicating with its electronic components, meaning it cannot process instructions to provide heat.

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 main board

What causes this fault?

This fault occurs when the boiler's main control center loses its electronic link with the rest of the internal components. The most common reason is a hardware failure within the printed circuit board itself or a loose connection in the internal wiring. Without this constant flow of data, the boiler cannot safely coordinate the sequence of ignition or pump activity, causing it to shut down immediately.

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

F10View →

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