33 High

Boiler Fault Code 33

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 33 appears across 9 boiler brands and 15 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 that the internal fan is not spinning at the required speed to safely clear waste gases, so it has shut down to prevent unsafe operation. (As reported on Vokera Linea HE)

Pick your boiler brand for the 33 fix

Alpha 33 2 models Baxi 33 2 models Gledhill 33 1 model Ideal 33 1 model Johnson Starley 33 1 model Main 33 2 models Potterton 33 1 model Unical 33 2 models Vokera 33 3 models

Source

Information for the 33 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