BoilerFaultCodes
The most common Baxi faults
Your boiler has detected a problem safely discharging exhaust gases or removing waste water, causing it to shut down for safety.
Why it happens: This fault occurs when the boiler's internal safety sensors detect that the exhaust gases are too hot or cannot escape the property correctly. It is often triggered by a breakdown in the sensor that monitors flue temperatures, or a physical blockage in the pipe that carries waste water away from the unit. When the system can no longer safely vent heat or clear condensation, it shuts down to prevent internal damage.
Check the external plastic condensate pipe for signs of freezing or blockageGently pour warm water over the external pipe if it is frozenEnsure the external flue terminal on your wall is not obstructed by debris or plantsReset the boiler once by turning the selector knob to 'R' for five seconds
Your boiler has reached an excessively high temperature and has shut down as a safety precaution to prevent damage.
Why it happens: This fault occurs when the water inside the boiler gets too hot, triggering a safety switch to shut the system down. The most common reasons are a pump failure preventing water from moving through the unit, or a internal blockage like air or sludge that is trapping heat in the heat exchanger.
Check that all radiator valves are fully open to allow water to circulate.Ensure your system pressure is between 1.0 and 1.5 bar on the front gauge.Try resetting the boiler by turning the selector knob to the 'R' position for five seconds.
Your boiler has lost water pressure and has stopped working to protect itself from damage.
Why it happens: This fault occurs when the water pressure inside your heating system drops below a safe level, causing the boiler to shut down to prevent overheating. The most common reason is a small leak in the pipework or radiators, though it can also happen if you have recently bled your radiators and haven't topped the water back up.
Locate the filling loop (the flexible braided hose) underneath or near the boiler.Slowly open the tap or valve(s) on the loop while watching the pressure gauge.Close the tap or valve(s) tightly once the gauge reaches between 1 and 1.5 bar.
Your boiler is struggling to move water around the system properly, which is causing it to shut down to prevent overheating.
Why it happens: This fault occurs when the boiler detects that water is not moving through the internal pipes quickly enough to take the heat away from the burner. The most common reasons are a failed pump that can no longer push the water, or a blockage caused by a build-up of sludge and debris in the system. Because the heat cannot escape, the boiler shuts down as a safety precaution to prevent the internal components from melting or cracking.
Check that all radiator valves (TRVs) are fully openEnsure your system pressure is between 1.0 and 1.5 bar on the gaugeTry resetting the boiler to see if the error clears
Your boiler is not receiving enough gas or is struggling to light the flame needed to heat your water and radiators.
Why it happens: This fault occurs when the boiler tries to ignite three times but fails to establish or maintain a steady flame. The most common reasons are an interruption in the gas supply, a blocked pipe, or a component inside the boiler being unable to create the spark needed to light the gas.
Check that your gas emergency control valve is open and any prepaid gas meter has credit.Ensure other gas appliances, like a hob, are working to confirm gas supply to the property.If it is freezing outside, check if your external condensate pipe has frozen and gently thaw it with warm water.Press the Reset button for five seconds to attempt to restart the boiler.
Your boiler has stopped working because the water pressure in the system has dropped too low.
Why it happens: This fault occurs when the water pressure inside your heating system drops below the minimum level required for the boiler to operate safely. The most common reasons are a slow leak from a pipe or radiator valve, or air being bled from the radiators without the system being topped back up with water.
Locate the filling loop (usually a silver braided hose with small lever valves under the boiler).Slowly open both lever valves to allow water into the system.Watch the pressure gauge and close both valves firmly once it reaches between 1.0 and 1.5 bar.
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 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.
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