BoilerFaultCodesThe 6 most common faults
01
b1 High Engineer
Your boiler's internal computer is failing to recognise a specific electronic memory chip that tells it how to operate correctly.
Full guide for b102
C6 High Engineer
Your boiler is struggling to push air through its system properly, which has caused it to stop working to keep you safe.
Full guide for C603
E2 High Engineer
Your boiler has lost the ability to accurately measure the temperature of the water used for your heating system, so it has safely shut down to prevent overheating.
Full guide for E204
E9 High Engineer
Your boiler has detected that it is overheating and has automatically shut itself down to prevent damage.
Full guide for E905
EA High Engineer
Your boiler has stopped working because it is unable to light the flame properly or keep it burning.
Full guide for EA06
F0 High Engineer
Your boiler has detected an internal software or electronic fault that prevents the system from operating safely.
Full guide for F0on the Worcester Bosch CDi Classic Regular
Code plugPrinted Circuit Board (PCB)Fan assemblyFlue assemblyNTC Temperature SensorNTC sensor
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 Worcester Bosch 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