BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water level inside the system has dropped too low to operate safely.
Locate the filling loop (usually a silver flexible hose) underneath the boiler.Slowly open the one or two taps on the hose until you hear water entering the system.Watch the pressure gauge and close the taps once the needle reaches between 1.0 and 1.5 bar.
Your boiler has failed to light the gas or cannot tell that the flame is burning, so it has shut down for safety.
Check if other gas appliances (like a hob) are working to ensure your gas supply is active.If you have a prepay meter, check that you have sufficient credit.Press and hold the Reset button for a few seconds to try restarting the boiler.
Your boiler has shut down because it has detected an unsafe build-up of heat, often caused by a blockage or poor water circulation.
Check if any radiator valves are closed and open them fully.Ensure the boiler pressure is between 1 and 1.5 bar on the gauge.Attempt to reset the boiler once it has cooled down.
Your boiler has detected a general problem and is waiting for a specific sub-code to appear to tell you exactly what is wrong.
Full guide for ALYour boiler has failed to ignite or stay lit, meaning it cannot produce heat or hot water.
Check if other gas appliances (like a hob) are working to ensure gas supply is activeEnsure your prepaid gas meter has credit if applicablePress and hold the 'R' or reset button for a few seconds to restart the ignition sequenceCheck that the condensate pipe outside hasn't frozen in cold weather
Your boiler has stopped working because the water pressure inside the heating system has dropped below the minimum level required to operate safely.
Locate the external filling loop, which is a silver braided hose connecting two pipes under the boiler.Open the small valve or tap on the loop to allow water into the system, watching the pressure gauge on the front of the boiler.Close the valve firmly once the needle on the gauge reaches between 1 and 1.5 bar, then check the boiler for the fault code to clear.
on the Sime Mia 30
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 Sime 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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
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