BoilerFaultCodesThe 6 most common faults
01
27 High DIY-safe
Your boiler has stopped working because it has detected that the water pressure inside the system is too low or the water pump is struggling to circulate water properly.
What to try first
Check your boiler's pressure gauge; if it is below 1 bar, you likely need to top up the system.Locate the filling loop (a silver flexible hose) underneath the boiler.Open the valves on the filling loop to let water in until the needle reaches 1.5 bar, then turn the valves off tightly.
02
24 High Engineer
Your boiler has stopped working because it cannot stay lit, likely due to a blocked pipe that drains away water created during the heating process.
Full guide for 2403
28 High Engineer
Your boiler is struggling to detect the temperature of the water it is trying to heat, so it has shut down your hot water supply to prevent overheating.
Full guide for 2804
29 High Engineer
Your boiler has stopped heating your radiators because it is receiving an incorrect or missing signal from the device that monitors water temperature.
Full guide for 2905
25 Emergency Engineer
Your boiler has detected dangerously high temperatures and has automatically shut itself down to prevent damage or fire risk.
Full guide for 2506
26 Emergency Engineer
Your boiler is struggling to clear exhaust gases safely, so it has shut itself down to prevent any harmful fumes from entering your home.
Full guide for 26on the Baxi Combi 105 HE
Central heating pumpPressure relief valvePressure sensorCondensate trapCondensate pipeIgnition electrode
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