BoilerFaultCodesBaxi Safety Thermostat neon Fault Code
Also written as SAFETYTHERMOSTATNEON — same fault.
The Baxi Safety Thermostat neon fault code means: your boiler has switched itself off because it got too hot, likely due to a circulation problem or a temporary blockage in the system.. It appears on 6 Baxi models in our database.
Technical description: The boiler has shut down in the event of the system or the boiler overheating.
DIY fix possible
Check that your pump is running and not stuck.Ensure all radiator valves and internal stopcocks are fully open.Wait for the boiler to cool down and then turn the selector switch to 'Reset' for five seconds.Check that your system pressure is correct (usually 1.0 to 1.5 bar) if you have a sealed system.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Baxi models that show the Safety Thermostat neon fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Baxi Safety Thermostat neon fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026