Worcester Bosch Greenstar 24i Junior Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2005-2013 Discontinued
GC Numbers 47-114-5347-311-8647-311-8747-311-9047-311-9147-406-54

Replaced by: Greenstar 25i

Download the Worcester Bosch Greenstar 24i Junior manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. 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 →

Fault codes

All 2 documented codes

Tap any card for details

Fast flash

Your boiler has detected a safety-related issue and has automatically shut itself down to prevent any risk while it waits for a manual reset.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
Full explanation for Fast flash
Slow flash

Your boiler has failed to light the flame, so it has safely shut itself down and requires you to manually reset it to try again.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Flame sensor
  • Gas valve
  • Printed Circuit Board
Full explanation for Slow flash
Status & diagnostic codes

4 operating states & engineer diagnostics

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

2 pulses Diagnostic Your boiler is currently in a manual testing mode set to operate at its minimum output, rather than running normally to heat your home. 2 pulses (No light) Diagnostic Your boiler has accidentally been set to a manual service mode and simply needs to be switched back to its normal operating setting. 5 pulses Diagnostic Your boiler is currently running at maximum capacity because the service mode has been activated, which is a setting used by engineers for testing processes. 5 pulses (No light) Diagnostic Your boiler isn't broken; it has simply been left in a manual 'test mode' used by engineers, and needs to be switched back to its normal setting.