BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside your heating system has dropped too low.
Locate the external filling loop (a silver braided hose) underneath the boiler.Open the valves at both ends of the hose to allow water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).Close both valves firmly and ensure the hose is disconnected if required by your specific installation.
Your boiler has detected that the water pressure inside your heating system is currently set too high for it to operate safely.
Locate a radiator in your home, preferably one upstairs.Using a radiator bleed key, carefully open the bleed valve to let a small amount of water out into a cloth or container.Monitor the pressure gauge on your boiler front panel until it returns to the green zone (typically 1.0 to 1.5 bar), then stop bleeding.
Your boiler is struggling to detect the temperature of the water used for your taps and showers, so it has stopped providing hot water to prevent any potential damage.
Full guide for ALL 04Your boiler has detected an issue with the sensor that measures the temperature of the water used for your radiators, meaning it has safely shut itself down to prevent overheating.
Full guide for ALL 05Your boiler has detected an internal safety fault and has stopped operating to prevent further damage.
Full guide for ALL 06Your boiler has detected that it is dangerously overheating and has automatically shut itself down to prevent damage.
Full guide for ALL 07on the Sime Murelle Elite HE 35T 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