BoilerFaultCodesThe 6 most common faults
Your boiler has detected that the water pressure is too low, which prevents it from heating up or providing hot water.
Locate the silver filling loop cable underneath your boiler.Slowly open the valve(s) to allow water into the system while watching the pressure gauge.Close the valve(s) firmly once the pressure gauge needle reaches between 1.0 and 1.5 bar.
Your boiler has stopped working because it cannot light the gas flame needed to provide heat and hot water.
Check that your gas emergency control valve is in the 'on' positionIf you have a pre-payment meter, check that you have sufficient creditPress the Reset button on the control panel to see if the boiler restarts
Your boiler has likely overheated or has air trapped inside, causing it to shut down for safety.
Locate the reset button on your boiler control panel and press it onceCheck that your radiator valves are open to ensure water can flow properlyBleed your radiators using a radiator key to remove any trapped air from the system
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 silver braided hose) underneath the boiler.Open the small valve(s) 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 valve(s) tightly and ensure the boiler resets.
Your boiler has detected a problem with its temperature sensor and has stopped working as a safety precaution.
Full guide for ALARM 05Your boiler has lost the ability to measure the temperature of the water being sent to your radiators, so it has shut down to prevent overheating.
Full guide for AL 05on the Sime iQE Comfort 30
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