BoilerFaultCodes
The most common Worcester Bosch faults
Your boiler is struggling to move water because there is air trapped in the system or the water pressure has dropped too low.
Why it happens: This fault occurs when the boiler detects that there is no water passing through the internal pump, causing it to spin without resistance. The most common reasons are a significant drop in system pressure or a large pocket of air becoming trapped inside the pump itself, which prevents it from being able to circulate heat. To protect the internal components from overheating or burning out, the boiler triggers a safety shutdown.
Check the pressure gauge and top up the system to 1.5 bar using the filling linkGently bleed air from your radiators using a radiator keyPress the reset button on the boiler control panel
Your boiler has lost its connection with the thermostat, meaning they are no longer speaking to each other to control your heating.
Why it happens: This fault occurs when the wireless link between your boiler and your wall thermostat is broken, preventing the boiler from receiving instructions to turn on. The most common reasons are dead batteries in the thermostat unit or an obstruction like a new piece of metal furniture blocking the radio signal between the devices.
Check if your thermostat batteries need replacingEnsure the thermostat is within range and has no obstructionsTurn the power to the boiler off and back on to restart the connection
Your boiler has sensed that it is getting too hot and has automatically shut down for safety.
Why it happens: This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety switch to kill the power. The most common reasons are a pump failure that stops water from moving around the system or a build-up of debris causing a blockage in the heat exchanger.
Check that your system pressure is between 1 and 1.5 bar on the front gaugeTop up the water pressure using the white internal or external filling loop if it is too lowEnsure all radiator valves are fully open and there are no blockagesPress the 'reset' button on the boiler control panel once pressure is corrected
Your boiler has stopped working because it cannot light a flame, most likely due to an interruption in the gas supply or a part that has worn out.
Why it happens: This fault occurs when the boiler tries to start up but fails to detect a steady flame after several attempts. The most common reasons are a temporary interruption in your gas supply, a build-up of carbon on the internal sensors, or a component failure like a worn-out ignition lead.
Check if other gas appliances, like a hob, are working to confirm your gas supply is onIf you have a prepaid meter, ensure you have sufficient creditPress and hold the 'Reset' button for five seconds to see if the boiler restartsIn freezing weather, check if your white plastic condensate pipe outside has frozen and gently thaw it with warm water
Your boiler's internal computer has encountered a glitch or a hardware failure, preventing it from running properly.
Why it happens: This fault occurs when the boiler's main control board loses its ability to process data correctly or experiences a communication breakdown between internal components. It is often caused by a sudden electrical surge, moisture entering the control box, or simply the natural degradation of the solder points and microprocessors over time.
Switch the boiler off at the fused spur or power switchWait 30 seconds and switch the power back onPress and hold the Reset button for 5 secondsIf the code persists, contact a Gas Safe engineer to inspect the internal electronics
Your boiler has encountered an internal communication error between its main electronic control boards, meaning it cannot currently function or heat your home.
Why it happens: This fault occurs when the boiler's two main 'brains'—the primary control board and the display board—stop talking to each other. It is usually caused by a loose internal connection, a glitch in the software, or a component failure on one of the electronic circuit boards. Think of it like a computer crashing because two internal parts can no longer share information.
Locate the power switch or fused spur for the boilerTurn the power off, wait for 30 seconds, and turn it back onPress the 'Reset' button on the boiler display once it restarts
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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.