BoilerFaultCodesThe 6 most common faults
01
A03 High Engineer
Your boiler has detected that it is overheating and has shut itself down as a safety precaution to prevent damage.
Full guide for A0302
A17 High Engineer
Your boiler is struggling to pump water around your heating system effectively, which prevents it from working properly.
Full guide for A1703
A18 High Engineer
Your boiler has detected that hot water is not flowing correctly through your radiators or pipes, meaning it has shut down to prevent itself from overheating.
Full guide for A1804
A33 High Engineer
Your boiler is having trouble pushing out exhaust gases, so it has safely shut itself down to prevent any risk.
Full guide for A3305
A97 High Engineer
Your boiler's main control computer is experiencing a communication error or internal fault that is preventing it from running properly.
Full guide for A9706
E 99 High Engineer
Your boiler has detected multiple failed attempts to function and has automatically locked itself out to prevent further issues.
Full guide for E 99on the Ariston Genus
NTC temperature sensorCirculation pumpHeat exchangerPressure sensorFlow sensorSystem filter
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Ariston shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue