BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the heating system has dropped below the minimum level required to operate safely.
Locate the external filling loop (a flexible silver hose) underneath the boiler.Open the small tap or valve on the filling loop to allow cold mains 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 the tap or valve tightly to stop the flow of water.
Your boiler has temporarily stopped working because it cannot detect water flowing through the system.
Check your boiler pressure gauge to see if it has dropped below 1 bar.Use the filling loop to top up the system pressure to around 1.2 to 1.5 bar.Reset the boiler using the reset button on the control panel.
Your boiler has detected that water is backing up inside the internal pipes because the waste pipe leading outside is likely blocked or frozen.
Locate the plastic condensate pipe where it leaves your property and goes outside.Check if the outdoor pipe is blocked by debris or frozen solid during cold weather.Pour warm (not boiling) water over the external pipe to thaw any ice and clear any blockages.
Your boiler has stopped because the water pressure inside the heating system has dropped too low to operate safely.
Locate the external filling loop, which is a silver braided hose connected between two pipes near your boiler.Open the valves at both ends of the hose to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly and remove the filling loop if required by your specific setup.
Your boiler has attempted to light the gas burner several times but has failed to detect a flame, causing it to shut down for safety.
Full guide for 06Your boiler has stopped working because it is unable to accurately measure the temperature of the water inside the system.
Full guide for ALL 05on the Sime Murelle Advanced HE MkII 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.
Affiliate links. We may earn a commission at no extra cost to you.