Worcester Bosch C7 fault codewhat it means and how to fix it
The fan is not running at all, as distinct from running at the wrong speed. The burner is locked out until it is fixed.
Take care
Get a Gas Safe registered engineer to look at your Worcester Bosch C7
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What C7 means
Worcester separate two fan conditions and it is worth knowing which you have. C6 means the fan speed is wrong — too low, or on some models too high. C7 means the fan is not running. That distinction narrows the diagnosis usefully: a fan turning at the wrong speed is usually a worn fan or a flue restriction changing its loading, whereas a fan not turning at all is more often electrical — a failed motor, a lost supply, or a broken connection.
The interlock behind both is the same and it is absolute. No condensing appliance will open its gas valve without proof that the fan is clearing combustion products through the flue, and there is no way to run around that. What a householder can usefully contribute is history: whether the appliance has been getting noisier over recent months, and whether anything obvious is blocking the flue terminal when viewed from the ground.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Fan motor failed | The most direct explanation for a fan that is not turning. Often the end point of months of increasing start-up noise. | Common |
| Fan seized mechanically | Bearings that have finally bound up rather than merely worn. Sometimes accompanied by a brief hum as the appliance tries to start it. | Common |
| Wiring or connector failure | No supply reaching the fan, or a broken connection in the harness. Considerably cheaper than a fan and worth eliminating first. | Occasional |
| Control board not driving the fan | The board is failing to energise it. Diagnosed once the fan and its wiring have been proved. | Occasional |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£200–£450
A replacement fan is typically £300 to £450 fitted on the Greenstar range. A wiring repair is a call-out charge of £80 to £150.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Worcester Bosch Greenstar fan assembly
87161431070£130–£250Authorised Worcester parts distributor
Price checked 28 September 2026
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Related Worcester Bosch fault codes
- C6 224Get it checkedThe fan is not reaching the speed the boiler asked for, so combustion cannot be confirmed as safe and the burner has been prevented from firing.Related: fan and flue
- D5Get it checkedThe condensate pump has failed or cannot discharge. Acidic water will back up inside the appliance, so it needs attention promptly.Related: fan and flue
- C1 264Get it checkedAirflow stopped part way through a firing cycle. The fan has quit or the flue is obstructed, and combustion gases may not be leaving safely.Related: fan and flue
- 2910Stop — call an engineerFault in flue system. The boiler has detected a problem with its flue and locked out. Worcester's checks are obstructions, the flue integrity test and water in the sump. Not a code to reset repeatedly.Related: fan and flue
- C4 273Usually simple to fixThe fan has run continuously for 24 hours, so the boiler has paused firing for two minutes as a precaution. Something has been calling for heat non-stop, and that is what to find.Related: fan and flue
- EA 227Stop — call an engineerThe boiler tried to light and never detected a flame, so it has shut the gas off and locked out. This is the most common Worcester fault code.Related: same brand
Own a Worcester Bosch boiler? Save it and its codes come first next time.
Related guides
Common questions about Worcester Bosch C7
What is the difference between C6 and C7?
C6 means the fan speed is wrong; C7 means the fan is not running. C6 more often turns out to be a worn fan or a flue restriction, while C7 skews towards an electrical failure. Quote whichever number you can actually see, because it changes where the engineer starts.
The boiler was grinding for months before this. Related?
Almost certainly. A fan bearing that grumbles on start-up and quietens as it spins up is wearing out, and a seizure is where that ends. Reporting that noise early turns an emergency into a planned repair.
Can I get heating any other way in the meantime?
Not from the boiler — the fan interlock blocks every burner operation including hot water. A plug-in electric heater for a day is the practical answer.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.