Worcester Greenstar fan faults: reading a code that has two halves
Worcester Greenstar boilers show a two-part code for fan faults. Learn how the display, the fault code, and the service manual fit together.
What this means
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.
Equipment and model context
Worcester Bosch Greenstar gas boilers using the two-part display and fault code convention described in Worcester service instructions
- Greenstar i combi
- Greenstar CDi Classic
- Greenstar Si Compact
- Greenstar 8000
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.
What you may notice
- Neither heating nor hot water is available, and the display shows two code elements rather than one.
- Either no fan sound accompanies a start attempt, or the fan runs briefly before everything stops.
- The appliance had become noticeably louder during operation over previous months.
Likely causes
- A fan motor or its bearings can degrade until the assembly cannot reach or hold the speed the appliance demands.
- The wiring carrying supply or speed feedback to the fan can break, corrode, or become unseated at a connector.
- Restriction in the fan housing or in the air path changes what the fan can achieve at a given input.
Diagnostic paths
Both code parts are visible on the display
The screen shows two distinct elements, which people often read as a single string or record only half of.
Photograph the display so both parts are captured together. The pair is what identifies the fault in Worcester service instructions, and half of it identifies almost nothing.
No fan sound at all during a start
Listening at the appliance during an attempt produces silence where a clear fan note used to be heard before ignition.
Record the silence and stop attempting further starts. A fan with no supply and a fan running below specification are different investigations.
It became noisier before it stopped
Operation had grown louder, rougher, or uneven over weeks or months, and the household had already remarked on it.
Give the engineer that history with an approximate start date. Bearing wear produces sound long before it produces a lockout.
Worcester diagnostics are a lookup rather than a translation. The pair from the display and the model from the data plate together select one row in the service instructions, and missing any of the three makes the lookup unreliable.
- Display codeThe first element on screen
- Fault codeThe second element on screen
- Data plateIdentifies the exact appliance
- InstructionsWhere the three resolve to one entry
| Element | What it narrows | Why both are needed |
|---|---|---|
| Display code | The broad area of the appliance | Too coarse alone |
| Fault code | The specific detected condition | Ambiguous without the first |
| Together | The entry in the service instructions | This is what an engineer looks up |
| Model number | Which instruction set applies | The same pair varies by generation |
Why half a code is worse than none
A homeowner who reports one element of a Worcester code has given the engineer something that looks like information and is not. The convention exists because the appliance has more conditions than a single short code could distinguish, so the two elements narrow it together. Searching the internet for one of them returns confident answers that may belong to a different pairing entirely.
Photographing the screen solves this completely and takes a second. It also captures the code before any reset erases it, which matters because the display is the only place the pairing appears.
Where a fan sits in a sealed appliance
On a Greenstar boiler, as on any room-sealed condensing appliance, the fan draws combustion air in through the flue and pushes the products back out through it. There is no natural draught to fall back on, so a fan that cannot run, or cannot be confirmed at the right speed, removes both the air supply and the exhaust route at once.
It also removes the ability to set a firing rate, because the gas valve meters against the air the fan delivers. That is why fan conditions produce a full lockout rather than reduced output. There is no low-output fallback to drop into, since the lowest output still requires a known quantity of air arriving at a known speed.
For a household this means the appliance is unavailable rather than degraded, and no amount of turning thermostats or programmers up will change that. The Worcester EA 227 page covers the ignition side of the same appliance, and the combi no hot water reference explains why both circuits stop together when a shared component is involved.
What to give the technician
Send the engineer a photograph of the display with both code elements, the model and serial number from the data plate, whether the fan is audible, and any history of increasing noise.
Safe homeowner 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.
Is a reset appropriate?
Worcester appliances allow a reset from the control panel, and one attempt shows whether the condition repeats. Reset before photographing the display and the pairing is lost.
When to call a 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.
Questions people ask about this
Why does my Worcester boiler show two codes?
Greenstar appliances present a display code and a fault code together, and the pair identifies one entry in the service instructions. Either element on its own does not resolve to a single condition.
Should I reset before or after photographing the code?
Photograph first. The display is the only place the pairing appears, and a reset clears it, which leaves the engineer without the identifier the service instructions are indexed on.
Can I get hot water while a fan fault stands?
No. The fan supplies combustion air and removes flue products for both circuits, so a combi produces neither heating nor hot water until the condition is resolved.
Evidence recordHow this page was checked
official manufacturer support article, operation manual · checked 2026-09-15
Every technical claim above was written from primary documentation held in the HVAC Bench evidence record: Worcester Bosch technical literature. Where a source limits a definition to certain models, test conditions, or product classes, that limit is repeated here rather than generalised.
- Documentation class
- official manufacturer support article, operation manual
- Scope of the definition
- Worcester Bosch Greenstar gas boilers using the two-part display and fault code convention described in Worcester service instructions
- Last checked
- 2026-09-15