BoilerFaultCodes F.688 High
Boiler Fault Code F.688
Also written as F688 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code F.688 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's internal computer is experiencing a communication breakdown, causing it to run in a limited, backup mode that may result in loss of heating or hot water. (As reported on Viessmann Vitodens 222-F B2TF)
Pick your boiler brand for the F.688 fix
Source
Information for the F.688 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026