BoilerFaultCodesThe 6 most common faults
Your boiler has switched itself off because it has reached too high a temperature, likely due to trapped air or a blockage stopping water from circulating.
Why it happens: This fault occurs when the water inside your boiler becomes too hot, causing a safety sensor to trip and shut the system down to prevent damage. The most common reason is that the water cannot move around the system properly, often due to an airlock in the pipework or a pump that has failed. It can also happen if your radiator valves are all closed or if there is a physical blockage restricting the flow.
Turn off the boiler and allow it to cool down completely.Use a radiator key to bleed all radiators to remove any trapped air.Check the boiler pressure gauge and top it up to 1.5 bar if it has dropped.Turn the boiler back on and press the 'Reset' button.
Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.
Why it happens: This fault occurs when the internal sensors detect that the water pressure has dropped below the minimum level required to circulate heat safely. The most common reason is a small leak somewhere in the central heating pipework or radiators, though it can also happen if you have recently bled your radiators without topping the system back up.
Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the one or two taps/valves on the filling loop until you hear water entering the system.Watch the pressure gauge until it reaches between 1.0 and 1.5 bar, then close the taps fully.
Your boiler has detected that water isn't moving through the system properly, which is causing it to overheat and shut down for safety.
Why it happens: This fault occurs when the boiler's internal sensors detect that the water temperature is rising too quickly because it isn't being moved away from the burner. The most common reason is a seized or failing pump, though it can also be caused by an airlock or a blockage in the system preventing the water from flowing. For your safety, the boiler shuts down immediately to prevent the heat exchanger from reaching dangerous temperatures.
Check that your system pressure is between 1 and 1.5 bar on the pressure gaugeEnsure all radiator valves and isolation valves under the boiler are fully openBleed your radiators to remove any trapped air pockets
Your boiler has tried to ignite but failed to stay alight, which is often caused by a lack of gas supply or a blocked condensation pipe.
Why it happens: This fault occurs when the boiler's control system attempts to light the burner but cannot detect a stable flame. The most common reasons are a temporary interruption in the gas supply, an ignition electrode that is too dirty to spark, or a blockage in the pipe that carries away waste water.
Check that your gas supply is turned on and you have credit on your meter.During freezing weather, check if your external white plastic condensate pipe is frozen and thaw it with warm water.Press the Reset button for five seconds.
Your boiler is struggling to move heated water through the system, causing it to shut down to prevent overheating.
Why it happens: This fault occurs when the water inside your boiler gets too hot too quickly because it isn't being pushed around your radiators fast enough. The most common reasons are a pump that has seized up or a build-up of sludge and debris that is physically blocking the pipework. Because the heat has nowhere to go, the boiler forces a shutdown to protect its internal components from heat damage.
Check that the boiler pressure is between 1.0 and 1.5 bar on the gaugeEnsure all radiator valves are fully openBleed your radiators to remove any trapped air pockets
Your boiler has stopped working because the water pressure in the central heating system has dropped too low.
Why it happens: This fault occurs when the water pressure inside your heating system falls below the minimum level required for the boiler to operate safely. The most common reason is a small leak somewhere in your radiators or pipework, but it can also happen if you have recently bled your radiators without topping the water back up.
Locate the filling loop (usually a silver flexible hose) underneath your boiler.Slowly open the one or two taps/levers on the hose until you hear water flowing.Watch the pressure gauge and close the taps once the needle reaches between 1 and 1.5 bar.
on the Baxi EcoBlue Advance
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 Baxi 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