Alpha CD C Fault codes & diagnostics

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

Combi Natural Gas 25-35 kW 2013-2018 Discontinued

Replaced by: E-Tec

Choose your boiler type

The CD C range comes in 3 types

Pick the one you have. The fault codes, GC numbers and manual differ by type.

CD25C 2 codes · 1 GC number CD28C 2 codes · 1 GC number CD35C 2 codes · 1 GC number
Each model has its own manual A family spans several manuals, one per model or generation. Pick your model above and its page has the manual its fault codes were read from.

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

Tap any card for details

Neon A flashing

Your boiler is struggling to circulate water properly, which means it has stopped heating your home to prevent potential internal damage.

High Engineer only £150-350 Shared across the CD C range

Parts commonly replaced

  • Circulation pump
  • Flow switch
  • System filter

Related codes

Full explanation for Neon A flashing
Neon B flashing

Your boiler has detected that it is getting too hot and has automatically switched itself off to prevent damage.

High Engineer only £120-250 Shared across the CD C range

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • Diverter valve
  • PCB
Full explanation for Neon B flashing