BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because it cannot light the gas required to provide heat or hot water.
Why it happens: This fault occurs when the boiler's control system attempts to light the burner but fails to detect a flame after several attempts. The most common reasons include a lack of gas reaching the unit, a worn-out ignition spark electrode, or a blockage within the burner system preventing the gas from catching light.
Check if your gas meter has credit and the isolation valve is openPress the reset button (the flame symbol with a cross) for five secondsWait for the boiler to restart and see if the fault clears
Your boiler has stopped because the water pressure inside the heating system has dropped too low.
Locate the filling loop (usually a silver braided hose with one or two valves underneath the boiler).Slowly open the valve(s) to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve(s) firmly once the correct pressure is reached.
Your boiler has stopped working because the water pressure inside the heating system has dropped too low.
Locate the filling loop, which is usually a flexible silver hose connected to two valves under the boiler.Open the valves slowly to allow water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close both valves tightly and ensure the pressure remains steady.
Your boiler is struggling to keep its flame lit while it tries to heat your home or water, causing it to shut down for safety.
Full guide for F4Your boiler is struggling to read the temperature of the water flowing through your heating system due to a loose or damaged electrical connection.
Full guide for F6Your boiler has lost the signal from one of its internal temperature sensors, causing it to stop heating to prevent potential overheating.
Full guide for F10on the Glow-worm Flexicom cx
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 Glow-worm 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