BoilerFaultCodes 67:40 Low
Boiler Fault Code 67:40
Also written as 6740 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 67:40 appears across 1 boiler brand and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler's solar heating accessory has detected a minor internal setting mismatch or a sensor communication issue regarding your hot water targets. (As reported on Viessmann Vitodens 300-W)
Pick your boiler brand for the 67:40 fix
Source
Information for the 67:40 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 27 April 2026