BoilerFaultCodesBritish Gas S.34 Fault Code
Also written as S34 — same fault.
The British Gas S.34 fault code means: your boiler has sensed very cold temperatures and has automatically turned on its built-in safety mode to prevent the internal pipes from freezing.. It appears on 1 British Gas model in our database.
Technical description: frost protection active (Priority 4). Temperature below 8O C - check thermistor connection if this is not true.
DIY fix possible
Check that your home heating is turned on or the thermostat is set to a reasonable temperature.Ensure any visible condensate pipes leading outside are not frozen or blocked.Wait for the boiler to finish its warming cycle; the code should disappear once the internal temperature rises.
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British Gas models that show the S.34 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
British Gas S.34 fault code information on this page is sourced and cross-checked against the official British Gas service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026