BoilerFaultCodesThe 6 most common faults
01
A02 High DIY-safe
Your boiler has stopped working because it has sensed that there is not enough water or water flow inside the heating system.
What to try first
Locate the filling loop under your boiler or near the pipework.Open the valves gradually to top up the system pressure until the pressure gauge reads between 1.0 and 1.5 bar.Close the filling loop valves tightly and reset the boiler.
02
A01 High Engineer
Your boiler has stopped working because it tried to light three times but failed to detect a flame.
Full guide for A0103
A07 High Engineer
Your boiler is struggling to stay lit and has failed to maintain a flame multiple times, causing it to lock itself out for safety.
Full guide for A0704
A33 High Engineer
Your boiler's internal mechanism for clearing waste gases is not working correctly, which forces the boiler to shut down for your safety.
Full guide for A3305
A97 High Engineer
Your boiler has detected an internal communication or electronic monitoring error and has safely shut down to prevent potential risks.
Full guide for A9706
A99 High Engineer
Your boiler's computer is experiencing a communication error or internal glitch, preventing it from operating reliably.
Full guide for A99on the Ariston ACO 27 MFFI
Circulating pumpPressure relief valveAutomatic air ventPressure switchIgnition electrodeGas valve
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