BoilerFaultCodesThe 6 most common faults
01
27 High DIY-safe
Your boiler has detected that water is failing to circulate properly, most likely because the pressure in your heating system has dropped too low.
What to try first
Check the pressure gauge on the front of the boiler; if it is below 1 bar, you need to repressurise the system.Locate the filling loop (a flexible metal or silver braided hose underneath the boiler) and open the valves until the gauge needle sits between 1 and 1.5 bar.Close the valves tightly and check the display to see if the error has cleared.
02
24 High Engineer
Your boiler has stopped working because it cannot light its internal flame or because the pipe that drains away waste water is blocked.
Full guide for 2403
26 High Engineer
Your boiler is struggling to clear exhaust gases safely, so it has shut down to prevent any risks.
Full guide for 2604
28 High Engineer
Your boiler is struggling to detect the temperature of the water it is trying to heat, which means you likely have no hot water available.
Full guide for 2805
29 High Engineer
Your boiler has stopped working because it is unable to accurately measure the temperature of the water being pushed to your radiators.
Full guide for 2906
FAN High Engineer
Your boiler has detected an issue with the internal ventilation system that prevents it from starting safely, meaning you currently have no heating or hot water.
Full guide for FANon the Baxi Combi 105 HE
Central Heating PumpPressure Relief ValvePressure SensorCondensate trapIgnition electrodeGas valve
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