Worcester Bosch CDi Classic Regular Fault codes & diagnostics

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

Regular Natural Gas 12-30 kW 2012-2020 Discontinued

Replaced by: Greenstar 8000 Life Regular

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

Severity at a glance

Each cell = one fault code. Hover to identify.
2 Emergency 6 High 1 Low

All 9 documented codes

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b1

Your boiler's internal computer is failing to recognise a specific electronic memory chip that tells it how to operate correctly.

High Engineer only £150-300

Parts commonly replaced

  • Code plug
  • Printed Circuit Board (PCB)
C6

Your boiler is struggling to push air through its system properly, which has caused it to stop working to keep you safe.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Flue assembly

Related codes

E2

Your boiler has lost the ability to accurately measure the temperature of the water used for your heating system, so it has safely shut down to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor

Related codes

E9

Your boiler has detected that it is overheating and has automatically shut itself down to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • NTC sensor
  • Primary heat exchanger
  • Pump
  • Diverter valve

Related codes

EA

Your boiler has stopped working because it is unable to light the flame properly or keep it burning.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Printed Circuit Board

Related codes

F0

Your boiler has detected an internal software or electronic fault that prevents the system from operating safely.

High Engineer only £200-450

Parts commonly replaced

  • Printed circuit board (PCB)
  • Control unit

Related codes

F7

Your boiler is detecting a flame inside even though it has been told to turn off, which means it cannot safely control its operation.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)
  • Flame rectification electrode

Related codes

FA

Your boiler has detected that a flame is still present even though it has attempted to turn the gas off, which indicates a potential safety issue with the internal gas valve.

Emergency Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Fd

Your boiler is simply indicating that the reset button has been triggered, likely by being pressed accidentally instead of the standard operation button.

Low DIY-safe

What to check first

  1. Wait for the boiler to cycle through its internal status check
  2. Ensure no buttons are currently obstructed or held down
  3. If the boiler does not return to normal operation, switch the unit off at the fused spur for 30 seconds and switch it back on

Related codes