BoilerFaultCodesThe 6 most common faults
01
Red LED on (solid) High DIY-safe
Your boiler has stopped working because it failed to light the flame after several attempts, usually due to a temporary interruption in the gas supply or a dirty ignition part.
What to try first
Check that your gas emergency control valve is open and you have credit on your gas meter (if applicable).Turn on another gas appliance, such as a hob, to ensure gas is flowing to the property.Press and release the reset button on the front of the boiler panel to restart the ignition sequence.
02
Red LED after flow switch High DIY-safe
Your boiler has detected that water is not circulating correctly through the system, causing it to shut down to prevent overheating.
What to try first
Check that the boiler pressure is between 1 and 1.5 bar on the pressure gaugeEnsure all radiator valves are fully open to allow water to flowCheck if any external valves on the pipework leading to the boiler have been accidentally closed
03
Flashing orange LED High Engineer
Your boiler is struggling to detect a flame, which means it will shut down for safety to prevent gas from flowing without being burned.
Full guide for Flashing orange LED04
Red LED on (after safety stat) High Engineer
Your boiler has shut down because it has detected internal temperatures that are too high, or a potential issue with the discharge of exhaust fumes.
Full guide for Red LED on (after safety stat)05
LED flashing after fan High Engineer
Your boiler has stopped working because the fan that clears away waste gases is not starting up or spinning correctly.
Full guide for LED flashing after fan06
Orange LED flashing High Engineer
Your boiler has detected an issue with the sensor that monitors central heating temperature, meaning it cannot safely regulate your radiators.
Full guide for Orange LED flashingon the Sime Ecomfort Plus HE
Ignition electrodeFlame sensing probeGas valveCirculation PumpWater Flow SwitchOverheat Thermostat (Limit Stat)
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