BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.
Locate the filling loop (a flexible silver hose) underneath the boiler or near the pipework.Slowly open the valves on both ends of the loop until you hear water entering the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (usually between 1.0 and 1.5 bar).Close both valves tightly and check that the boiler restarts automatically.
Your boiler has detected that the water pressure inside the heating system is currently too high, which prevents it from operating safely.
Locate a radiator in your home that has a bleed valve.Place a cloth and a container under the valve.Use a radiator key to slowly release air and a small amount of water until the pressure gauge on the front of your boiler returns to the green zone (typically 1.0 to 1.5 bar).
Your boiler has detected that water is not flowing around your heating system properly, so it has shut down to prevent damage.
Check your central heating pressure gauge; if it is below 1 bar, use the filling loop to top it up to 1.5 bar.Ensure all radiator valves are fully open.Turn the boiler off and on again using the reset button to see if the error clears.
Your boiler's temperature sensor is providing incorrect readings or has disconnected, which has caused the system to shut down to prevent overheating.
Full guide for ALL 05Your boiler has attempted to start but is unable to detect a flame, causing it to shut down for safety.
Full guide for ALL 06Your boiler has detected that it has become dangerously hot and has shut itself down to prevent any damage or safety issues.
Full guide for ALL 07on the Sime Murelle Advanced HE Combi
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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