High
F.66 on Vaillant ecoTEC plus Aquaplus

Your boiler's control panel has lost communication with the main internal computer, preventing the boiler from receiving instructions on how to operate.

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

Display fault | Display defect; fault in the connection to the display; electronics defect

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

F.67View →

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