Alpha 500e Fault codes & diagnostics

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

Combi Natural Gas 24 kW Discontinued

The fault code is already on your display

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

Just want the most common Alpha 500e faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

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Overheat thermostat

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

High Engineer only £120-220

Parts commonly replaced

  • Overheat thermostat
  • Central heating pump
  • Diverter valve
  • PCB
Full explanation for Overheat thermostat
Red reset button illuminated

Your boiler has stopped working because it failed to ignite, which could be due to a simple issue like a lost gas supply or a more complex internal fault.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board
Full explanation for Red reset button illuminated
White reset neon illuminated

Your boiler has sensed a lack of water flow, which is preventing it from heating your home safely.

High Engineer only £150-250

Parts commonly replaced

  • Flow switch
  • Diverter valve diaphragm
  • Central heating pump
Full explanation for White reset neon illuminated