BoilerFaultCodesThe 6 most common faults
01
27 High DIY-safe
Your boiler is struggling to circulate water, likely because there is not enough water inside the system or the internal pump has stopped working.
What to try first
Check your pressure gauge; if it is below 1 bar, top up your boiler using the filling loop until it hits 1.5 bar.Turn off the power to the boiler for 30 seconds to perform a hard reset.Check if any radiators are cold at the bottom, which may indicate trapped air needing a bleed.
02
24 High Engineer
Your boiler is failing to light the internal flame, which could be due to a blockage in the waste water pipe or an issue with the gas ignition system.
Full guide for 2403
29 High Engineer
Your boiler has stopped working because it is unable to accurately measure the temperature of the water used for your radiators.
Full guide for 2904
neon flashing High Engineer
Your boiler has detected a general internal fault that prevents it from starting, meaning you currently have no heating or hot water.
Full guide for neon flashing05
25 Emergency Engineer
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage or dangerous overheating.
Full guide for 2506
26 Emergency Engineer
Your boiler is struggling to clear exhaust gases safely, so it has turned itself off to prevent any risk of fumes entering your home.
Full guide for 26on the Baxi 105e
Central heating pumpPressure gaugePressure relief valveIgnition electrodeFlame rectification probeCondensate trap assembly
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