3x High

Boiler Fault Code 3x

Also written as 3X — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed

Fault code 3x appears across 1 boiler brand and 3 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 a problem with how it vents exhaust gases or manages air flow, causing it to shut down for safety. (As reported on Vokera Linea HE)

Pick your boiler brand for the 3x fix

Vokera 3x 3 models

Source

Information for the 3x 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