Worcester Bosch Error Codes & Diagnostics
Complete diagnostic directory for official Worcester Bosch fault codes. Verify root causes, safe troubleshooting steps, and replacement part numbers before calling a technician.
Worcester Bosch E9 219 fault code: heating safety overheat
Worcester Bosch assigns E9 with cause code 219 to the central heating safety temperature limiter having tripped, meaning the flow temperature at the heat exchanger climbed past its allowed limit. It points at heat not moving away from the exchanger fast enough, from a circulation, pump, or fouling problem, rather than at a single failed part. Applies to: Worcester Bosch Greenstar boilers that pair E9 with cause code 219 This reading follows Worcester Bosch Greenstar literature that displays a fault code alongside a cause code and lists 219 as the safety temperature limiter. Other Worcester ranges and other E9 cause codes can differ, so record both numbers together before acting. Owner-safe checks: Note both numbers, E9 and 219, and the time the lockout appeared, then leave the boiler switched off rather than cycling the reset. | Check that any labelled isolation valves under the boiler are open and in the same position as normal, without removing covers. Qualified technician: Pump, flow sensor, heat exchanger, safety limiter, and system flushing work all require a Gas Safe registered engineer, and the boiler should stay off until then.
Worcester Greenstar Si Compact EA 227 ignition fault
On the documented Worcester Bosch Greenstar Si Compact ErP, EA with subcode 227 means no ionisation was detected after ignition. The user instructions permit the Reset button once and require service if the alert returns. The display does not prove whether flame failed to form or formed without valid sensing. Applies to: Greenstar Si Compact ErP This EA 227 definition is for Greenstar Si Compact ErP user instructions 6 720 813 279. Other Greenstar models attach different three-digit subcodes to EA, so record both lines of the display. Owner-safe checks: Photograph EA and 227 together, perform only the user-manual reset once, and note whether stable operation returns without opening the case. Qualified technician: Returning EA 227, gas, combustion, ionisation, electrode, vent, condensate, grounding, and sealed-case work require a Gas Safe registered engineer.
Worcester Greenstar fan faults: reading a code that has two halves
Worcester Greenstar boilers report faults as a display code and a fault code together, and the pair is what identifies the condition. Fan-related entries in that convention describe the appliance being unable to establish or confirm the fan speed it requires, which prevents combustion because gas is metered against the air the fan delivers. Applies to: Worcester Bosch Greenstar gas boilers using the two-part display and fault code convention described in Worcester service instructions Worcester uses the two-part convention across the Greenstar range but the specific pairing differs between models and generations. Record both parts exactly as the display shows them and match them against the service instructions for the model on your appliance data plate rather than a list compiled elsewhere. Owner-safe checks: Photograph the display so that both code elements are captured, along with anything else shown on screen. | Copy the full model name and serial number from the data plate, which is behind or beneath the casing flap on most Greenstar appliances. | Listen during one start attempt and note whether a fan is audible and for how long. Qualified technician: Diagnosing and replacing a boiler fan, and testing its wiring and feedback, are Gas Safe registered tasks on a room-sealed appliance. | The casing forms part of the sealed enclosure between combustion and the room, so it is not removed for inspection by an occupant.