BoilerFaultCodesThe 6 most common faults
Your boiler has detected that the water pressure inside your heating system is too low to operate safely, or the water is not circulating correctly.
Check your external pressure gauge to confirm it reads below 1 bar.Locate the external filling loop (usually two silver valves with a flexible hose between them).Open the valves slowly to allow water into the system until the pressure gauge reaches 1.5 bar, then turn the valves off tightly.
Your boiler has shut down because the internal water temperature has become too hot while trying to provide hot water.
Check that the radiator valves and the main boiler valves are fully openEnsure the central heating system pressure is between 1.0 and 1.5 barReset the boiler using the control knob to see if the fault clears
Your boiler has failed to light the gas flame, meaning it has shut itself down for safety and cannot provide heating or hot water.
Check if your gas supply is active by testing another gas appliance like a hob.Perform a reset by turning the control knob to 'R' for five seconds and then back to the on position.Verify that your condensate pipe (the plastic pipe leading outside) isn't frozen if it is currently winter.
Your boiler has stopped working because it cannot light its internal flame, which means you currently have no heating or hot water.
Full guide for Er01Your boiler has detected that it is overheating and has automatically shut down to prevent damage or dangerous pressure buildup.
Full guide for Er02Your boiler's internal computer has encountered a critical error and cannot safely operate the heating or hot water systems.
Full guide for Er03on the Biasi ActivA 18S
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 Biasi 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