BoilerFaultCodesThe 6 most common faults
Your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.
Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Open the one or two taps on the filling loop slowly while watching the pressure gauge.Close the taps firmly once the needle reaches between 1.0 and 1.2 bar.Reset the boiler using the selector dial to clear the fault code.
Your boiler is failing to light the gas or cannot detect that it has successfully lit a flame.
Check that your gas supply is turned on at the meterIf you have a prepaid meter, ensure you have sufficient creditCheck if other gas appliances, like a hob, are working correctlyReset the boiler by turning the selector switch to the reset position for a few seconds
Your boiler has switched itself off because it has detected that it is getting too hot, which is a safety mechanism to prevent damage.
Ensure your radiator valves are fully open to allow water to circulateCheck if your system water pressure is between 1 and 1.5 bar on the gaugeGently bleed your radiators to remove any trapped air from the systemReset the boiler by turning the selector switch to the reset position for a few seconds
Your boiler has stopped working because water that normally drains away is backed up, often due to a blocked or frozen exterior pipe.
Check the plastic condensate pipe outside for ice or blockages.If frozen, pour warm (not boiling) water over the pipe to thaw it.Restart the boiler using the reset button once the pipe is clear.
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 60 minutes.After one hour has passed, the lock-out should clear automatically or allow one further reset.If the boiler immediately fails again, do not attempt further resets and call a Gas Safe engineer to find the underlying fault.
Your boiler has lost its connection to your smart thermostat or external control panel, meaning it cannot receive the correct signals to turn on and off.
Check that your wall thermostat or remote control has power and fresh batteries.Ensure the thermostat is within range of the boiler and has not been moved.Reset the boiler by turning the selector switch to the 'R' position for a few seconds.
on the Sime Dewy 30/50 HE WM
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