The blower went on my A4, became intermittent and then wouldn't work at all. Apparently this is a fairly common failure on older vehicles as it's on all the time, the brushes wear out and you can't get replacements so you have to replace the whole blower motor.
The blower is produced by Valeo and is part no. 8D2 820 021. Audi want £300 for one, but you can get the exact same part from independents at half the cost.
There was a guy on ebay selling some of them a whiole back, but I got mine from Audi4U on 01278-434141.
It's really easy to fit, just remove the glovebox and you'll see the blower. You have to remove a metal bracket to get to it then it's just 4 screws and it's out.
You can check that it is the brushes by opening up the blower unit and cleaning the brushes with WD40 and it should start working again, but only for a week or so.
