BoilerFaultCodesThe 5 most common faults
Your boiler has stopped working to protect itself and simply needs to be restarted to clear a temporary error.
Why it happens: This fault happens when the boiler tries to light the flame but fails to detect one after several attempts. It is usually caused by a temporary interruption in the gas supply or a worn-out component that struggles to create the initial spark. To keep you safe, the system shuts down completely until it is manually told that it is okay to try again.
Turn the main On/Off switch to the '0' positionWait for at least five secondsTurn the switch back to the 'I' position to restart the boiler
Your boiler has stopped working because it cannot get a steady supply of gas to stay lit.
Why it happens: This fault occurs when the boiler tries to light the flame but fails to detect one, causing the system to shut down for safety. The most common reasons are a temporary interruption in your gas supply, worn-out ignition parts that can no longer create a spark, or a faulty internal valve that isn't opening properly.
Check if other gas appliances, like a cooker, are working to confirm your gas supply is active.If you have a prepayment meter, check that you have enough credit.Locate your gas meter and ensure the main handle is in the 'on' position.Reset the boiler by turning the main selector dial to 'Reset' for five seconds, then back to your preferred setting.
Your boiler has detected a blockage in the exhaust pipe or a problem with the fan, causing the system to shut down for safety.
Why it happens: This fault occurs when the boiler's safety sensors detect that harmful exhaust gases are not being cleared from the system effectively. The most common reasons are a mechanical failure of the fan, a blockage in the external flue pipe, or a perished internal seal that is leaking air.
Check the external flue pipe (the white pipe on your outside wall) for any visible obstructions like bird nests, leaves, or debris.Ensure there are no items such as garden furniture or plants blocking the airway of the flue.If the exterior is clear, do not attempt to open the boiler; you must call a Gas Safe engineer to inspect the internal fan and air pressure switch.
Your boiler has detected that there is not enough water in the heating system to operate safely.
Why it happens: This fault occurs when the water pressure inside your heating system drops below a safe level, preventing the boiler from firing up to protect the internal components. The most common reasons for this are a leak somewhere in the pipework or radiators, or simply needing to top up the system after bleeding air from your radiators.
Locate the filling loop (usually a silver flexible hose) underneath or near the boilerSlowly open the tap or taps on the filling loop to allow water into the systemMonitor the pressure gauge until it reaches between 1 and 1.5 bar, then close the taps fully
Your boiler is failing to switch into summer mode due to an internal electronic circuit board failure.
Why it happens: This fault occurs when the internal electronic components responsible for registering button presses on the control panel have degraded or failed. The most common reason is a physical breakdown of the circuitry on the printed circuit board, which prevents the boiler from acknowledging the command to switch modes.
Full guide for Summer mode LEDon the Glow-worm Compact
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