BoilerFaultCodes Alert High
Boiler Fault Code Alert
Also written as ALERT — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Alert 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 has detected an internal error and is waiting for you to look at the display to reveal the specific fault code causing the problem. (As reported on Worcester Bosch Greenstar Heatslave II)
Pick your boiler brand for the Alert fix
Source
Information for the Alert 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