BoilerFaultCodesThe 6 most common faults
Your boiler has attempted to start but could not light the internal flame, so it has shut down to prevent gas from building up.
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 has detected that it is overheating and has shut itself down to prevent damage because it cannot circulate water properly.
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 stopped working because the water pressure inside the heating system has dropped too low to operate safely.
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 external filling loop, which is a small silver flexible hose connecting two pipes near the boiler.Open the valves at both ends of the hose to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly and ensure the hose is disconnected if required by your specific setup.
Your boiler has detected that hot water is not flowing around your heating system correctly, which is causing it to shut down to prevent overheating.
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 attempted to start but failed to detect a flame, causing it to stop operating to ensure your safety.
Why it happens: This fault occurs when the boiler successfully lights, but the internal sensors lose track of the flame while it is running, causing the system to shut down for safety. The most common reasons are a worn-out sensing probe that can no longer 'see' the fire, or an unstable gas supply that prevents the flame from staying consistent.
Check that your gas pre-pay meter has creditEnsure other gas appliances in your home are working to confirm gas supplyPress the 'Reset' button for five seconds
Your boiler has detected that it is getting too hot or that water isn't moving through the system correctly, causing it to shut down for safety.
Why it happens: This fault occurs when the internal sensors detect that the water temperature inside the boiler has exceeded safe limits, triggered by a lack of circulation. The most common reasons are a failed pump that isn't pushing water around the system, or a blockage caused by a build-up of debris or air. In some cases, the sensors themselves may have become faulty and are providing an incorrect reading to the control board.
Check that your radiator valves are openEnsure your system water pressure is between 1 and 1.5 bar on the gaugeReset the boiler by turning the selector switch to 'R' for five seconds
on the Baxi EcoBlue System
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