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 external filling loop (the flexible silver hose) usually found underneath the boiler or nearby.Open the one or two taps on the filling loop slowly until you hear water moving.Watch the pressure gauge on the boiler until it reaches between 1.0 and 1.2 bar, then close the taps fully.
Your boiler has failed to light, which means it cannot provide the heat or hot water you need.
Check if other gas appliances, like a hob, are working to ensure gas is reaching the houseCheck if your gas meter has credit (if using a prepayment meter)Hold the 'Reset' button for 3 seconds to attempt a restart
Your boiler has switched itself off because it has detected that the water inside is getting too hot.
Check that your radiator valves are open and not turned to zero.Attempt to reset the boiler by turning the selector switch to the reset position and back.Ensure your system pressure is correct if a gauge is visible, and bleed any air from your radiators.
Your boiler has detected that waste water cannot drain away properly, likely due to a blockage in the outlet pipe or internal trap.
Check if the external white plastic drain pipe has frozen during cold weather.If frozen, pour warm (not boiling) water over the external pipe or apply a heat pack to thaw it.Ensure the internal condensate trap is not visibly blocked with debris.Reset the boiler once the blockage is cleared.
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 but do not touch any buttons for at least 1 hour.After 60 minutes have passed, the lockout will clear automatically.Attempt one single reset to see if the original fault has cleared.
Your boiler has lost its connection to your smart thermostat or external heater controls, meaning it cannot receive instructions to turn on.
Check that your wall thermostat is powered on and has fresh batteries if applicable.Ensure the thermostat wiring or receiver box is securely plugged in and hasn't been accidentally bumped.Turn the boiler power off and back on at the fused spur switch to attempt to re-establish the connection.
on the Sime Brava Slim HE Regular
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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