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 flexible silver filling loop under or near the boiler.Slowly open the one or two small taps on the loop until you hear water entering.Watch the pressure gauge and close the taps firmly once the needle reaches between 1.0 and 1.2 bar.
Your boiler is failing to light properly, which means you currently have no heating or hot water.
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 and the isolation valve is open.Press and hold the 'Reset' button for 3 seconds to attempt a restart.
Your boiler has switched itself off to prevent overheating, usually because the water isn't moving through the system correctly or there is trapped air.
Check that your radiator valves and isolation valves under the boiler are fully open.Bleed all radiators to remove any trapped air that might be causing a blockage.Attempt to reset the boiler by turning the selector knob to the 'R' position for a few seconds.
Your boiler is struggling to detect a flame, which means it cannot stay lit to provide heating or hot water.
Check if other gas appliances (like a hob) are working to confirm your gas supply is active.If you have a prepayment meter, check that you have sufficient credit.Try to reset 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 around the system correctly, which could be due to a blockage or a stuck pump.
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 that might be blocking flow
Your boiler has failed to stay lit after six attempts and has shut down to prevent damage, possibly due to a fuel supply issue or a faulty internal sensor.
Check if other gas appliances (like a hob) are working to confirm your gas supply is active.If you have a prepay meter, check that you have sufficient credit.Press and hold the 'Reset' button for 1 to 5 seconds to attempt a restart.
on the Sime Brava 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.
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