Newbie with a ABS warning light - cannot find fault!!

[Sandgroper]

Hello all and hoping someone can help a newbie!  New love is my recently purchased 2003 A4 B6 3L convertible.  ABS warning light on when I bought her - had the ABS module taken out and sent off to be checked - no issues with the unit itself.  Brakes ok, rear brake lights changed, wheel sensors all ok.  Brake fluid changed.  Does anyone have any ideas where the faulty presumably wire might be?  Also is it true that if ABS isn't working it just reverts to normal brakes just watch out in ice, snow, heavy rain? Thanks!!

[Magnet]

Hello Susan,

Thanks for being in touch with the forum. 
Not sure why the ABS module was suspected - a bit like going for the most complex issue first! 
Most ABS issues on cars of that age are due either to one of the individual ABS sensors, or the signalling to the sensors. 
You say ‘wheel sensors all OK’. Could you let us know how you have confirmed that. 

Although I’m not a fan of diagnostics, in this case plugging it in should identify which ‘wheel’ is the offending one. This will obviously allow you to further investigate where the issue is with that wheel. 
Personally I would change the sensor on that wheel (using Bosch or Febi if not genuine VAG). If the situation persists then the fault is likely to be with the hub ‘magnetic’ signalling. Not sure on yours, but if you cannot see any tooth wheel or collar arrangement on the shaft, then it’s most likely to be a weak magnet in the hub. If so, this is built into the hub and the offending hub will need to be replaced - I would fit a  complete hub and bearing assembly, rather than swopping old bearings into a new hub.

Hope this helps. Perhaps you could let us know how you get on. 
Kind regards,

Gareth.