OK I don't know how experienced you are but on my boiler the fan bearing seized after 7 years. So my hunch is that this is the problem. If you can get someone to take the fan out, with no electricity a good one will spin freely with no noise and I would guess yours will be stiff and difficult to turn. Either buy a new fan, or it is possible to replace the bearings. It's quite nasty having a fan not working so I suggest you get it done before using it; gas residues are not extracted from the boiler.
eduk
October 2013
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