BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the system is too low.
Locate the silver braided filling loop hoses underneath or near your boiler.Slowly open the one or two taps/levers on the filling loop until you hear water flowing.Watch the pressure gauge and close the taps once it reaches between 1.0 and 1.2 bar.
Your boiler has failed to light the flame, which means it cannot heat your water or radiators.
Check if other gas appliances in your home, like a hob, are working to confirm gas supply.Ensure your gas meter has credit if you use a pre-payment meter.Press the 'Reset' button on the boiler control panel to see if it restarts.
Your boiler has overheated because the water temperature inside the unit has reached an unsafe level, causing it to shut down for safety.
Check that all radiator valves are fully open to allow water to circulate.Inspect the system pressure gauge and top up to 1.5 bar if it is too low.Try to reset the boiler by turning the selector dial to the 'R' position for a few seconds.
Your boiler is having trouble detecting a flame, which prevents it from firing up to provide heating or hot water.
Check that your gas emergency control valve is in the 'on' positionIf you have a prepay gas meter, ensure it has sufficient creditCheck if other gas appliances in your home, like a hob, are working correctlyPress the 'Reset' button on the boiler control panel
Your boiler has stopped heating because water is not moving through the system properly.
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 openGently bleed your radiators to ensure there is no trapped air blocking the flow
Your boiler has shut down because the internal water drainage system is backed up or blocked, often due to a frozen or clogged outlet pipe.
Locate the plastic pipe leading from your boiler to the outside drain.Check if the end of the pipe is frozen; if so, pour warm (not boiling) water over it to melt the ice.Inspect the pipe for any physical debris or kinks that may be stopping the water flow.Reset the boiler once the blockage is cleared.
on the Sime Murelle Pro HE R MkII System
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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