What it means
Newer Greenstar i ErP and Compact ErP boilers show a number under C6: C6 215 means the fan is running too fast, and C6 216 too slow.
What to check, in order
- Don't try to fix it yourself
Worcester's manual says not to try to put C6 right yourself.
- Call a Gas Safe registered engineer
Tell them the code on the display.
When to call a Gas Safe engineer
Worcester's service booklet lists a loose fan connector, a mains voltage outside tolerance, a damaged fan cable, a failed fan or a faulty control board.
A repair visit will usually check the fan, its wiring and the flue.
- Note the model and serial number. They're on a label on the data badge, usually under the boiler or behind the front cover.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Quick answers
What does the Worcester Bosch C6 fault code mean?
The boiler's fan isn't turning at the right speed, so the boiler has stopped. On the Greenstar CDi Classic, C6 means the fan is too slow. Newer Greenstar i ErP and Compact ErP boilers show a number under C6: C6 215 means the fan is running too fast, and C6 216 too slow.
Can I fix Worcester Bosch C6 myself?
Engineer only (engineer visit). Start with: don't try to fix it yourself; call a Gas Safe registered engineer. Worcester's service booklet lists a loose fan connector, a mains voltage outside tolerance, a damaged fan cable, a failed fan or a faulty control board.
Is Worcester Bosch C6 worth repairing?
Get a quote first. It can be as simple as a loose connector, but a new fan or control board costs more, so ask for a price first.
Checked against
- Worcester Bosch Greenstar CDi Classic user instructions (PDF)
- Worcester Bosch Greenstar CDi Classic engineer's service booklet (PDF)
- Worcester Bosch Greenstar i ErP installation and servicing instructions (PDF)
- Worcester Bosch Greenstar Si Compact ErP installation and servicing instructions (PDF)
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.