Alpha C23 Fault codes & diagnostics

2 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 23 kW Discontinued

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Fault codes

All 2 documented codes

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LED / flash-pattern codes
Neon B Flashing very slowly

Your boiler is currently stuck in a standby or waiting mode because it is receiving power but has not been triggered to start heating.

Low DIY-safe

What to check first

  1. Check your room thermostat or smart controller settings to ensure they are calling for heat
  2. Increase the temperature setting on your thermostat to see if the boiler fires up
  3. Check if the boiler's own internal hot water or heating dials are turned up sufficiently
Full explanation for Neon B Flashing very slowly
Digital codes
A Illuminated continuously

Your boiler has attempted to start but is unable to ignite its internal flame, meaning your heating and hot water will not work.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
Full explanation for A Illuminated continuously