BoilerFaultCodesThe 5 most common faults
01
Neon A flashing High Engineer
Your boiler has lost the ability to accurately measure its own internal temperature, which causes it to shut down to prevent the system from getting too hot.
Full guide for Neon A flashing02
Neon B flashing High Engineer
Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage.
Full guide for Neon B flashing03
E01 High Engineer
Your boiler is failing to light the flame, which means it cannot produce any heating or hot water for your home.
Full guide for E0104
E02 High Engineer
Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage.
Full guide for E0205
E03 High Engineer
Your boiler has detected an issue with the ventilation system that clears exhaust gases, so it has safely shut itself down to prevent unsafe operation.
Full guide for E03on the Alpha CD S
NTC SensorWiring harnessOverheat thermostatCentral heating pumpDiverter valvePCB
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