BoilerFaultCodesThe 6 most common faults
Your boiler has switched itself off because it has detected it is getting too hot, usually caused by the water pressure being too low.
Why it happens: This fault occurs when the internal safety sensor detects that the heat exchanger has become dangerously hot, causing the boiler to shut down to prevent damage. The most common reason is a lack of water circulating through the system, often due to low pressure, a blockage, or a pump failure. If there isn't enough water to carry the heat away to your radiators, the temperature inside the unit rises too quickly.
Check the pressure gauge on the front of the boiler or the digital display.Locate the filling link (usually a blue lever underneath the boiler or a white plastic key).Slowly top up the water pressure until it reaches between 1.0 and 1.5 bar.Press the 'Reset' button on the boiler display to clear the fault.
Your boiler is failing to light the flame properly, meaning you will not have any heating or hot water until the issue is resolved.
Why it happens: This fault occurs when the boiler's internal computer tries to start a fire but cannot detect a stable flame. The most common reasons are a lack of gas reaching the burner, dirty sensors failing to 'see' the flame, or a fault within the electronic control board that manages the ignition process.
Check if your gas supply is working by testing other gas appliances like a hobEnsure your gas meter has credit if you use a pre-payment meterPress the Reset button on the boiler display panel once to attempt a restart
Your boiler has stopped working because the water pressure is too low and needs to be topped up.
Why it happens: This fault occurs when the system loses too much water, preventing the boiler from circulating heat safely. The most common reasons are a slow leak from a radiator valve or the natural loss of pressure that happens after you bleed your radiators. If the pressure looks normal on the gauge but the code persists, the internal sensor that reads the water level may be blocked or broken.
Locate the integrated filling link (blue levers) or the external filling loop underneath the boilerSlowly open the valves until you hear water moving and watch the digital display or pressure gaugeClose the valves firmly once the pressure reaches between 1.0 and 1.5 bar
Your boiler has shut down because the water inside is getting much hotter than it should be, which is often caused by a blockage or a pump failure preventing the heat from moving away.
Why it happens: This fault happens when the water leaving the boiler heats up too quickly or exceeds safe limits, causing the system to shut down for safety. It is usually caused by a pump failure or a blockage within the pipes that prevents hot water from circulating away from the boiler's heat exchanger. In many cases, it is the result of 'sludge' or debris building up over time and restricting the flow of water.
Check that all radiator valves are fully open to allow water to circulate.Ensure your boiler pressure gauge is between 1 and 1.5 bar; top up if necessary.Check if any external bypass valves or magnetic system filters are blocked.
Your boiler is heating up too quickly and has shut down to prevent damage, usually because water isn't flowing through the system fast enough.
Why it happens: This fault occurs when the water inside the boiler heats up much faster than the system can carry it away, causing the internal safety sensors to shut the unit down. The most common reason is a blockage or a failing pump preventing the hot water from circulating through your radiators. It can also be triggered if your radiator valves are all closed or if there is excessive air trapped in the pipework.
Check that your radiator valves (TRVs) are fully open and not stuck.Ensure the blue filling loop handle is closed and the system pressure is between 1 and 1.5 bar.Restart the boiler using the reset button on the display panel.
Your boiler has detected that the water pressure in your radiators is falling much faster than expected, which could indicate a significant leak.
Why it happens: This fault occurs when the boiler detects a sudden and significant loss of water pressure within the central heating circuit. It is usually caused by a large leak in the pipework or a failure in internal components like the expansion vessel, which forces water out of the system. The boiler shuts down as a safety precaution to prevent the internal heat exchanger from overheating without enough water to cool it.
Check all visible radiator valves and pipework for signs of water leakingTop up the system pressure to between 1 and 1.5 bar using the internal filling linkRestart the boiler to see if the code clears and the pressure remains stable
on the Worcester Bosch Greenstar 8000 Life & Style
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 Worcester Bosch 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
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