BoilerFaultCodes 4 green High
Boiler Fault Code 4 green
Also written as 4GREEN — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 4 green 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 temperature sensors are stuck in a mode that is telling the system to stay on, which can lead to overheating or your heating staying on when it shouldn't. (As reported on Ferroli Combi 77 FF Popular)
Pick your boiler brand for the 4 green fix
Source
Information for the 4 green 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