Alpha CD24 Fault codes & diagnostics

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

CombiSystem Natural Gas 24 kW 2006-2010 Discontinued
GC Numbers 41-532-0241-532-0641-532-0847-532-1947-532-21

Replaced by: CD24R

Download the Alpha CD24 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Fault codes

All 2 documented codes

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C1

Your boiler has detected a faulty internal sensor that monitors water temperature, causing the heating system to stop working for safety.

High Engineer only £100-£180

Parts commonly replaced

  • Primary Return NTC Temperature Sensor
  • Sensor Wiring Harness

Related codes

Full explanation for C1
Neon D

Your boiler has lost power or has an internal electrical fault, meaning it cannot provide any heating or hot water until an electrical issue is resolved.

High Engineer only £120-£350

Parts commonly replaced

  • Main PCB
  • Internal Fuse
  • Main Terminal Block

Related codes

Full explanation for Neon D
Status & diagnostic codes

1 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

Neon D illuminated Status Your boiler is receiving power correctly and is currently in its normal standby state.