BoilerFaultCodesThe 6 most common faults
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 started to heat up but the flame went out unexpectedly while it was running.
Why it happens: This fault occurs when the boiler's control system loses the signal that a flame is present while it is already firing. The most common reason is that the flame sensing electrode has become worn or dirty and can no longer detect the heat, although it can also be caused by an unstable gas supply or a failing component preventing the gas from flowing correctly.
Check that your gas emergency control valve is fully openIf you have a prepaid gas meter, check that you have sufficient creditAttempt to reset the boiler by turning the selector switch to 'R' for five seconds
Your boiler's internal pump is struggling to move water around the system before the burner starts, which often suggests an air lock or a blockage.
Check that your radiator valves and isolation valves under the boiler are fully openBleed all radiators to remove trapped air that might be blocking the flowEnsure the system pressure is between 1.0 and 1.5 bar on the pressure gauge
Your boiler has switched itself off because it has detected that the water inside has become far too hot.
Check that your radiator valves are open and not turned to zero.Ensure there is enough pressure in the system (typically between 1 and 1.5 bar).Turn the selector switch to the reset position for five seconds and then back to 'onn'.
Your boiler has stopped working because the water pressure in the system has dropped too low to operate safely.
Locate the filling loop (usually a silver braided hose with small taps) underneath the boiler.Open both taps slowly until you hear water entering the system and watch the pressure gauge.Close both taps tightly once the needle reaches between 1.0 and 1.5 bar.
Your boiler has detected that water is not moving through the system properly, which is causing it to overheat and shut down for safety.
Check that your system pressure is between 1 and 1.5 bar on the gaugeEnsure all radiator valves and isolation valves under the boiler are fully openBleed all radiators to remove trapped air pockets
on the Baxi Duo-tec Combi GA
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