Worcester Bosch 24 CBi Fault codes & diagnostics

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

Combi Gas 2000 onwards Discontinued
GC Number 41-311-48
Download the Worcester Bosch 24 CBi manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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 →

Severity at a glance

Each cell = one fault code. Hover to identify.
8 High
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
41-311-48 24 CBi RSF 2000–2001

Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.

Just want the most common Worcester Bosch 24 CBi faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 8 documented codes

Tap any card for details

LED / flash-pattern codes
Flashing light

Your boiler has failed to light the gas or cannot stay lit, meaning your heating and hot water have stopped working.

High DIY-safe £90-280

What to check first

  1. Check if your gas supply is active by testing another gas appliance like a hob.
  2. Ensure your credit is topped up if you have a pre-payment gas meter.
  3. Press the reset button on the boiler control panel for 5 seconds.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Probe
Full explanation for Flashing light
Digital codes
FAULT POINT A

Your boiler has completely lost power, meaning the display and all internal functions have shut down.

High DIY-safe £90-250

What to check first

  1. Check that the main fused spur switch next to the boiler is turned on.
  2. Go to your home's fuse box or consumer unit to check if the boiler circuit breaker has tripped, and reset it if necessary.
  3. Check that the plug (if applicable) is securely plugged into the socket.

Parts commonly replaced

  • PCB
  • Fuse
  • Power supply lead
Full explanation for FAULT POINT A
FAULT POINT B

Your boiler is receiving a signal for heating or hot water, but the burner is failing to ignite.

High Engineer only £150-£350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for FAULT POINT B
FAULT POINT C

Your boiler is attempting to start up, but the burner is only partially lighting or failing to stay fully lit.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Circuit board

Related codes

Full explanation for FAULT POINT C
FAULT POINT D

Your boiler has completely stopped working and locked itself down for safety reasons because it failed to ignite.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for FAULT POINT D
FAULT POINT E

Your boiler has completely stopped working and locked itself out as a safety precaution, meaning you currently have no heating or hot water.

High Engineer only £100-£250

Parts commonly replaced

  • Ignition lead
  • Electrodes
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for FAULT POINT E
FAULT POINT F

Your boiler has registered an unusual system error that isn't covered by the standard fault codes, meaning it has temporarily shut down for safety.

High Engineer only £100-£300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Internal Wiring Harness
  • Main Control Assembly

Related codes

Full explanation for FAULT POINT F
Steady light

Your boiler has switched itself off because it has become too hot to operate safely.

High DIY-safe £90-180

What to check first

  1. Check that your radiator valves are open to allow water to flow.
  2. Wait for the boiler to cool down completely.
  3. Press the reset button once to see if the system restarts.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Thermistor

Related codes

Full explanation for Steady light