The PCB (printed circuit board) is the primary control module of the Worcester Bosch Greenstar boiler. It manages ignition sequencing, gas valve modulation, fan speed control, pump operation, and the full safety interlock chain. When a Greenstar PCB fails, the boiler is rendered inoperative — and the fault code it throws often gives a strong indication of exactly which PCB function has stopped working.
Fault Codes Indicating PCB Failure
The most direct PCB fault indicator on a Worcester Bosch Greenstar is a persistent EA fault combined with confirmed-functional ignition components. EA normally indicates ignition failure — but if the electrode is intact, the ignition lead is undamaged, and gas supply is confirmed, the fault is typically the PCB’s ignition drive circuit.
Other indicators of PCB failure include:
- Boiler fails to respond to thermostat signals despite a correct wiring check
- Boiler resets but doesn’t stay running regardless of system condition
- Multiple intermittent fault codes with no consistent component fault
- No display, no function — completely dead boiler with mains power confirmed
Before condemning the PCB: A comprehensive diagnostic approach rules out simpler faults first. Ignition leads, electrodes, and gas valve operation should all be tested before the PCB is confirmed as the failing component. PCBs are expensive — unnecessary replacement is a costly mistake.
PCB Part Numbers by Model
Worcester Bosch PCBs are model-specific. Always confirm the exact model before ordering.
Common Greenstar PCB part numbers:
- 87483004610 — Greenstar CDi Compact (24–38kW variants)
- 87483002370 — Greenstar CDi Classic
- 8716118413 — Greenstar 24i/28i Junior
- 87483004660 — Greenstar 27i Junior
For all other models, locate the 8-digit part number on the existing PCB label or call our helpline with the model number: 0330 124 5678.
OEM vs Compatible PCBs
Worcester Bosch PCBs are safety-critical components directly connected to the gas circuit and ignition system. We stock and recommend OEM (original equipment manufacturer) PCBs only for Worcester Bosch Greenstar boilers.
Installation Notes
Worcester Bosch PCB replacement must be carried out by a Gas Safe registered engineer. After PCB replacement:
- Confirm all wiring connectors are fully seated
- Restore mains power and check for fault codes
- Carry out a full ignition sequence check
- Test all safety cutouts (overheat stat, pressure switch)
- Record the replacement in the boiler’s service history
Need a Recommended Installer?
PCB replacement is a Gas Safe engineer job. Our Recommended Installers cover Worcester Bosch Greenstar repair across the full range:
- HGB Heating Kent — Gas Safe engineers, Worcester Bosch specialists, Kent and Medway
- Boiler Sense — Certified boiler specialists, Kent and South East London