BoilerFaultCodesThe 3 most common faults
01
Neon D NOT illuminated High DIY-safe
Your boiler has no power, meaning it cannot start up to provide heating or hot water because it is not receiving any electricity.
What to try first
Check your consumer unit to see if the boiler's circuit breaker has trippedEnsure the fused spur switch located near the boiler is turned onCheck the fuse inside the fused spur switch to see if it has blown
02
Neon A flashing High Engineer
Your boiler is struggling to circulate water properly, which means it has stopped heating your home to prevent potential internal damage.
Full guide for Neon A flashing03
Neon B flashing High Engineer
Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent damage.
Full guide for Neon B flashingon the Alpha CD C
Fused spur switchPCB (Printed Circuit Board)Wiring harnessCirculation pumpFlow switchSystem filter
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 Alpha 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