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 silver filling loop (braided hose) usually found underneath the boiler.Slowly open the small valve handles to allow water into the system.Watch the pressure gauge and close both valves once it reaches between 1.0 and 1.2 bar.
Your boiler has stopped working because it cannot light the gas or cannot detect that a flame has started.
Check if your gas supply is active by testing another gas appliance like a hob.Ensure your gas emergency control valve (usually by the meter) is open.Press and hold the 'R' or reset button for a few seconds to restart the ignition sequence.
Your boiler has switched itself off because it has detected that the internal water temperature is too high, often caused by trapped air or a blockage preventing water flow.
Check that your radiator valves are open to ensure water can circulate.Carefully bleed your radiators to remove any trapped air from the system.Attempt to reset the boiler by turning the selector dial to the 'R' position for a few seconds.
Your boiler has detected that waste water cannot drain away properly, usually because the discharge pipe is blocked or the internal trap is full.
Locate the plastic pipe leading from the boiler to the outside drain.Check if the end of the pipe is submerged in water or blocked by debris/ice.If the pipe is frozen, gently pour warm (not boiling) water over it to melt the ice.Restart the boiler using the reset button.
Your boiler has been manually reset too many times in a short period and has temporarily locked itself for safety.
Leave the boiler powered on and do not touch any buttons for 60 minutes.After one hour has passed, the lockout will clear automatically.Attempt one final reset; if the original fault returns, do not attempt further resets and call an engineer.
Your boiler has lost its connection to the smart thermostat or remote control, meaning it is not receiving instructions on when to turn the heating on.
Check that your smart thermostat or remote controller is powered on.Replace batteries in the wall thermostat if applicable.Restart your home internet router if the thermostat relies on Wi-Fi.Ensure any modular receivers plugged into the boiler are pushed in firmly.
on the Sime Brava Slim HE 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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