Worcester Bosch C6 Fault Code: Fan Speed Too Low
Hertfordshire, Bedfordshire & Cambridgeshire
C6 on a Worcester Bosch means the fan is not running at the speed the boiler expects, so the appliance has shut down.
There is nothing safe for a homeowner to check on this one. The fan sits inside the sealed combustion chamber.
What C6 actually means
The fan drives combustion air in and flue gases out. The PCB monitors its speed and will not let the burner light unless the fan is running correctly.
If the reported speed is wrong, the boiler stops. It will not risk burning gas without proven ventilation, which is exactly what you want it to do.
What you can safely check yourself
Do not remove the boiler casing. The combustion chamber is sealed for a reason and disturbing it is a Gas Safe activity.
Nothing. The fan is inside the appliance casing, in the sealed combustion circuit, and opening that up is Gas Safe work.
The one thing worth doing is looking at the flue terminal outside. If it is obviously obstructed by nesting material, leaves or snow, clearing that is reasonable. Anything beyond that is engineer work.
When to stop, and why
Stop after checking the outside flue terminal. If C6 persists, call a Gas Safe engineer.
What causes it beyond the simple checks
A worn fan bearing, a failed fan, a loose or corroded fan cable connector, low or unstable mains supply voltage, a blocked or restricted flue, or a PCB that is not reading the fan signal correctly. The service booklet has the engineer check the fan connector first, then the supply voltage, before condemning the fan.
How Vantage can help
We are Gas Safe registered under 956889 and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day. Call us on 01462 506374. See also boiler repair and boiler servicing.
Frequently asked questions
Can I run the boiler with C6 showing?
No. It will not run, and that is deliberate.
Is it always the fan?
No. A loose connector or a supply voltage problem will produce the same code, which is why it gets tested rather than guessed at.
Is a fan an expensive repair?
It is a common enough part and usually straightforward to change. You should get a price before the work starts, which is how we do it.
Related fault codes
Other Worcester Bosch codes: EA · E9 · A1 · F0 · all Worcester Bosch codes. See also boiler repair and boiler not firing up.
In Worcester Bosch’s own words
The Greenstar CDi Classic engineer’s service booklet lists C6 as: Fan speed too low.
Worcester Bosch use different code sets across their ranges and generations. The definition above is taken from the Greenstar CDi Classic service booklet. If your boiler is a different model and the code behaves differently, check the manual for your appliance or ring us and we will tell you what it means on your unit.
When to call an engineer
If the checks above have not cleared it, the next steps are engineer work and the boiler should not be reset repeatedly in the meantime. Call Vantage Plumbing and Heating on 01462 506374. We are Gas Safe registered under 956889, the line is answered by a person at any hour of any day, and you get a price before anyone starts.
Need help today?
Call and speak to a person, any hour, any day of the year. Get a fixed price quote or call 01462 506374.
Need help today?
Call and speak to a person, any hour, any day of the year, or get a fixed price quote online.
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Vantage Plumbing and Heating covers Hertfordshire, Bedfordshire and the surrounding areas. Call and talk to an engineer, or send us the details and we will come back to you with a price.
Gas Safe registered, number 956889. Emergency line answered 24/7.