BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure is too low and needs to be topped up.
Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the valve or valves on the filling loop until you hear water flowing.Watch the pressure gauge on the front of the boiler and close the valves once the needle reaches between 1.0 and 1.2 bar.
Your boiler has switched itself off because it has detected that the water inside is getting too hot.
Check that all radiator valves are fully openBleed all radiators to remove trapped air from the systemOnce the boiler has cooled down, try to restart it by pressing the 'R' reset button
Your boiler is struggling to detect a flame, which means it cannot stay lit to provide heating or hot water.
Check that your gas meter is turned on and other gas appliances are workingPress and hold the 'R' Reset button for several seconds to restart the systemEnsure your condensate pipe has not frozen if the weather is extremely cold
Your boiler has detected a problem with the sensor that monitors the temperature of the water being sent to your radiators, which prevents it from heating up correctly.
Full guide for AL 05Your boiler has failed to light the flame or maintain it, causing it to shut down for safety reasons.
Full guide for AL 06Your boiler has detected an issue with an internal sensor or a settings mismatch, which is preventing it from running properly.
Full guide for AL 10on the Sime Brava DGT HE
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