BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water level inside the system is too low and needs to be topped up.
Locate the silver braided filling loop hoses underneath or near your boilerSlowly open both small valves on the filling loop until you hear water flowingWatch the pressure gauge and close both valves firmly once the needle reaches between 1.0 and 1.2 bar
Your boiler has too much water pressure in the system, which causes it to shut down for safety.
Locate a radiator bleed valve and use a key to release water into a cloth or container.Monitor the boiler's pressure gauge until it drops down into the green zone, ideally 1.2 bar.Ensure the filling loop valves are fully closed so no more water enters the system.Turn the boiler off and back on to reset the fault code.
Your boiler has failed to light the flame, which means you will have no heating or hot water until the issue is resolved.
Check if other gas appliances in your home, like a hob, are working to confirm your gas supply is active.Verify that your gas meter has credit if you use a prepay meter.Press the 'Reset' button on the boiler control panel to see if the lockout clears.
Your boiler has overheated, causing a safety sensor to automatically shut the system down to prevent damage.
Wait for the boiler to cool down completelyCheck that all radiator valves are open and not blockedPress the 'Reset' button on the boiler control panelCheck the system pressure gauge is between 1.0 and 1.5 bar
Your boiler is struggling to detect a flame, meaning it cannot stay alight and providing you with no heating or hot water.
Check that your gas emergency control valve is in the 'on' positionIf you have a prepayment meter, check that you have sufficient creditTry resetting the boiler by turning the selector switch to the reset position for a few seconds
Your boiler has stopped working because water is not moving through the system properly, which is preventing it from heating up safely.
Check that your system pressure is between 1 and 1.5 bar on the pressure gaugeEnsure all radiator valves and isolation valves under the boiler are fully openTry bleeding your radiators to remove any trapped air pockets
on the Sime Murelle EV HE Combi
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