BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Locate the filling loop (usually a silver braided hose with small valves) underneath the boiler.Slowly open both valves to allow water into the system while watching the pressure gauge.Close both valves firmly once the needle reaches between 1.0 and 1.5 bar.
Your boiler has failed to light the flame, which means it cannot provide you with any heating or hot water at the moment.
Check if other gas appliances, like a hob, are working to ensure gas is reaching the property.Verify that your gas meter has credit if you use a pre-payment meter.Ensure the gas stopcock (yellow valve) is in the open position.Press the 'Reset' button on the boiler control panel once to see if it clears the fault.
Your boiler has switched itself off because it has detected that the internal water temperature has become too hot.
Check that all radiator valves are fully openEnsure the system water pressure is between 1 and 1.5 bar on the pressure gaugePress and hold the 'R' (Reset) button for a few seconds to restart the boilerBleed any air from your radiators
Your boiler has stopped working because water isn't moving through the system as it should, often due to a pump issue or a blockage.
Check that your system pressure is between 1.0 and 1.5 bar on the gaugeEnsure all radiator valves and isolation valves under the boiler are fully openRestart the boiler using the reset button to see if the pump clears itself
Your boiler has stopped working because the internal pipe that drains away waste water is likely blocked or full.
Locate the external plastic pipe leading from the boiler and check if the end is frozen or blocked by debris.Carefully pour warm (not boiling) water over any frozen sections of the external pipe.Reset the boiler by turning the selector dial to the 'R' position for a few seconds.
Your boiler has been reset too many times in a short period and has now locked itself for one hour as a safety precaution.
Full guide for AL 28on the Sime Murelle One 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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.