Worcester 30 CDi boiler ?

Fan motor failed or PCB.

Which you'll have seen when you did a Google search for yourself, I'm sure.

Check the second to last entry here:

http://www.upperplumbers.co.uk/plumbing/plumbing_pages.php?title=Worcester&cat=12

Mentioned in the manual here - download and keep

https://www.worcester-bosch.co.uk/support/document/download/release/6720812177/12515

XXX
January 2016