4 Red Flashes High

Boiler Fault Code 4 Red Flashes

Also written as 4REDFLASHES — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 4 Red Flashes appears across 2 boiler brands and 23 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected an issue with the ventilation fan, which means it cannot safely clear exhaust fumes and will not ignite. (As reported on Main MainEco)

Pick your boiler brand for the 4 Red Flashes fix

Baxi 4 Red Flashes 21 models Main 4 Red Flashes 2 models

Source

Information for the 4 Red Flashes 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