BoilerFaultCodesThe 6 most common faults
01
E08 High DIY-safe
Your boiler has detected that the water level inside the heating system is too low to operate safely.
What to try first
Locate the filling loop (a silver braided hose) underneath the boilerOpen the valves on the filling loop to allow cold mains water to enter the system until the pressure gauge reads between 1.0 and 1.5 barClose the valves firmly and check for any visible leaks on your radiators
02
A01 High Engineer
Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent internal damage.
Full guide for A0103
AA01 High Engineer
Your boiler has failed to light the flame after repeated attempts and has safely shut itself down to prevent a gas buildup.
Full guide for AA0104
AA02 High Engineer
Your boiler is failing to ignite because it cannot detect that the flames have successfully warmed up the water inside the system after three attempts.
Full guide for AA0205
AA07 High Engineer
Your boiler has tried and failed to light the gas flame several times, so it has safely shut itself down to prevent a build-up of unburnt gas.
Full guide for AA0706
AA21 High Engineer
Your boiler is failing to detect the water flowing through it, which prevents it from igniting to heat your home or water.
Full guide for AA21on the Ariston Ecogenus 24 MFFI
Filling loopPressure sensor/transducerPressure relief valveNTC thermistorPrimary heat exchangerPump
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