BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside your heating system has dropped too low to operate safely.
Locate the external filling loop (a flexible silver hose connecting two pipes near the boiler)Open the valves at both ends of the hose to allow water into the systemMonitor the pressure gauge on the boiler until it reaches 1.5 barClose both valves tightly and remove the hose if required
Your boiler has detected that the water pressure inside the system is too low to operate safely.
Locate the external filling loop, which is usually a flexible silver hose connected to two valves beneath the boiler.Slowly open the valves to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly and ensure the pressure gauge remains steady.
Your boiler is struggling to push water around your heating system, which is often caused by trapped air, a blockage, or a pump that has stopped working.
Check your boiler pressure gauge and top it up to 1.5 bar if it is below 1 bar.Bleed all radiators in your home to ensure there is no trapped air preventing flow.Ensure all radiator valves are fully open to allow water to circulate freely.
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Full guide for 01Your boiler has detected a fault with the sensor responsible for measuring the temperature of your hot water, so it has shut down to prevent incorrect operation.
Full guide for 04Your boiler has stopped working because it is unable to accurately measure the temperature of the water being sent to your radiators.
Full guide for 05on the Sime Murelle EV 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