BoilerFaultCodesThe 6 most common faults
Your boiler has failed to light, which means it cannot heat your water or your home, usually due to a lack of gas or a problem with the ignition spark.
Check if other gas appliances in your home, such as a hob, are working to confirm your gas supply is active.If you have a prepaid meter, ensure you have sufficient credit available.Press and hold the 'R' or Reset button for 5 seconds to see if the boiler restarts.
Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.
Check that your radiator valves are open and not turned to zeroEnsure there is enough water pressure in the system (usually 1.0 to 1.5 bar)Wait for the boiler to cool down and press the 'Reset' button
Your boiler has detected that the water pressure in the system is too low to run safely and has shut down as a precaution.
Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Open the filling valves slowly until you hear water entering the system.Watch the pressure gauge and close the valves once the needle reaches between 1.0 and 1.5 bar.
Your boiler has shut down because it is getting too hot too quickly, usually because the water isn't moving through the system properly.
Check that your radiator valves and any external isolation valves are fully openEnsure there is enough water pressure in the system (typically 1.0 to 1.5 bar)Try resetting the boiler to see if the error clears
Your boiler has stopped working because it cannot light the gas flame or the flame has gone out unexpectedly.
Check if other gas appliances, like a hob, are working to ensure gas is reaching the property.If it is freezing outside, check that the white plastic condensate pipe leading outdoors isn't frozen.Press and hold the red 'Flame Failure' reset button for five seconds to see if the boiler restarts.
Your boiler has switched itself off because it has become too hot internally, often due to a temporary blockage or a circulation issue.
Check that your radiator valves are openEnsure there is enough water pressure in the system (usually 1.0 to 1.5 bar)Press the white Reset button on the front control panel
on the Baxi Promax Ultra
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