High
F.77 on Vaillant ecoTEC plus System

Your boiler has detected an issue with the system responsible for removing exhaust gases or draining away the water produced during the heating process.

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

Flue gas flap/condensate pump fault

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.22View →F.75View →

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