BoilerFaultCodesThe 6 most common faults
01
neon illuminated High Engineer
Your boiler's electronic control panel is experiencing an internal fault, causing a warning light to stay on and likely preventing your heating or hot water from working.
Full guide for neon illuminated02
Fan runs at max. speed High Engineer
Your boiler's fan is running continuously at top speed, which indicates the internal computer has detected a safety concern and is trying to vent the system.
Full guide for Fan runs at max. speed03
Spark at ignition electrodes High Engineer
Your boiler is attempting to light but is struggling to complete the ignition process, preventing your heating or hot water from working correctly.
Full guide for Spark at ignition electrodes04
Neon B flashing High Engineer
Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.
Full guide for Neon B flashing05
Neon A flashing High Engineer
Your boiler has lost the ability to accurately measure its internal temperature, so it has safely shut down to prevent overheating.
Full guide for Neon A flashing06
Red reset button illuminated High Engineer
Your boiler has stopped working because it failed to ignite, so it has automatically shut down for safety.
Full guide for Red reset button illuminatedon the Alpha CD28
Neon PCBMain PCBPrinted Circuit Board (PCB)Fan assemblyAir pressure switchIgnition electrode
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