BoilerFaultCodesThe 6 most common faults
Your boiler has lost water pressure and has shut down as a safety precaution.
Why it happens: This fault occurs when the water level inside the central heating system drops below a safe threshold, often due to a small leak in the pipework or a radiator. It can also happen if air has been bled from the radiators recently or if the internal expansion vessel has lost its charge, causing water to escape through the safety valve. Without enough water pressure, the boiler cannot circulate heat safely and shuts down to prevent the heat exchanger from overheating.
Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the tap or taps on the filling loop until you hear water entering the system.Monitor the pressure gauge until it reaches between 1.0 and 1.5 bar, then turn the taps off tightly.The red light should stop flashing and the boiler should restart.
Your boiler has encountered a general operation error and needs to be restarted to resume heating and hot water.
Why it happens: This fault occurs when the boiler's internal computer detects an interruption in the normal operating sequence, causing it to shut down for safety. The most common reasons include a failure to sense a flame correctly or a momentary communication error between the electronic components. If the reset doesn't work, it usually indicates that a part like the ignition lead or the main circuit board is failing to send the correct signals.
Locate the On/Off switch on the boiler control panelTurn the switch to the '0' positionWait for five secondsTurn the switch back to the 'I' position to reset the unit
Your boiler has stopped working because it cannot light the gas flame or it can't detect that the flame is lit.
Why it happens: This fault occurs when the boiler attempts to start up but fails to establish a flame after several attempts. The most common reasons include a lack of gas reaching the unit, worn-out spark electrodes that can no longer ignite the fuel, or a faulty sensor that fails to tell the boiler the flame is safely lit.
Check if other gas appliances in your home, like a hob, are working to confirm gas supply.If you have a prepaid gas meter, ensure it has sufficient credit.Press the reset button on the boiler control panel once to see if it restarts.
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Why it happens: This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety sensor to cut the power. The most common reasons are a pump failure that stops water from moving or a blockage in the heat exchanger that traps heat inside the unit.
Check that all radiator valves are open and not turned off.Ensure there is enough water pressure in the system (typically between 1 and 1.5 bar).Press the reset button on the control panel once the boiler has cooled down.
Your boiler's main control screens are having trouble talking to each other, which means the boiler doesn't know what settings you are asking for.
Why it happens: This fault occurs when the communication link between the boiler's internal computer and the front display panel is broken. It is usually caused by a loose connection cable or internal electrical wear on one of the circuit boards, which prevents your instructions from reaching the burner.
Turn off the electrical power supply to the boiler at the fused spur switch.Wait approximately 60 seconds for the electronics to fully discharge.Turn the power back on to see if the communication link resets.
Your boiler has become too hot and has shut down as a safety precaution to prevent damage.
Why it happens: This fault occurs when the water inside the boiler exceeds a safe temperature limit, causing the system to shut down to protect its internal components. The most common reasons are a failed pump that isn't moving water away from the heat exchanger quickly enough, or a blockage in the pipework restricting flow.
Check that your radiator valves are open to allow water to flow.Ensure there is enough pressure in the system by checking the gauge (it should be around 1.5 bar).Gently bleed your radiators to remove any trapped air that might be blocking circulation.
on the Glow-worm Ci Range
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