F.77
Vaillant fault code
Vaillant F.77: flue non-return flap or condensate pump fault
Engineer only
Vaillant describes F.77 on ecoTEC plus boilers as: flue non-return flap or condensate pump fault. Possible causes Vaillant lists, for an engineer to check: no response from the flue non-return flap, or condensate pump defective.
What you can safely do
There is nothing you can safely do yourself with this one. Leave the boiler off and book an engineer.
Call a Gas Safe engineer if
- Book a Gas Safe registered engineer.
Find a Gas Safe engineer near you
Opens the official Gas Safe Register search.
Applies to: ecoTEC plus. Codes can differ between models, so check your manual.