Boiler Fault Code Test 3

Also written as TEST3 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026

Fault code Test 3 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 that the internal mechanism responsible for clearing exhaust gases is not operating correctly, so it has safely shut down to prevent any unsafe build-up. (As reported on Vokera Hydra)