BoilerFaultCodesThe 6 most common faults
Your boiler has failed to light the flame and has locked itself out for safety.
Check if other gas appliances in your home (like a hob) are working to ensure gas supply is active.Check your gas meter to ensure it has credit if you use a prepay meter.Press the 'Reset' button on the control panel to attempt a restart.
Your boiler has switched itself off because the water inside the heat exchanger has become too hot to operate safely.
Wait 20 to 30 minutes for the water temperature to cool down naturally.Check that your radiator valves are fully open and there is no air trapped in the system.Press the Reset button once the unit has cooled to see if the error clears. If it recurs immediately, call an engineer.
Your boiler has stopped working because the water pressure is too low for the system to circulate heat safely.
Locate the filling loop (usually a silver braided hose with small valves underneath the boiler).Slowly open both taps/levers on the filling loop to allow water into the system.Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close both taps tightly.
Your boiler is unable to light the gas burner to provide heating or hot water and has shut down for safety.
Check if other gas appliances, like a cooker, are working to ensure gas is reaching the property.Ensure your gas meter has credit if you use a pre-payment meter.Press the 'Reset' button on the control panel to attempt a restart.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Locate the flexible silver filling loop underneath or near your boiler.Slowly open the small tap(s) on the loop to allow water into the system.Watch the pressure gauge and close the taps firmly once it reaches 1.5 bar.
Your boiler has shut down because it has detected that the water inside the system has become dangerously hot.
Locate the reset button (usually marked 'R') on the control panel and press it.Ensure all radiator valves are fully open to allow water to flow freely.Check that your system pressure is between 1.0 and 1.5 bar on the gauge and top up if necessary.
on the Ariston Excalibur
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