Right, the 92 Cabriolet (Rabbit) inline four in my '84 has this set up on
the alternator adjustment arm and it does break, right at the end of
the 'gear rack' (as in Rack and pinion tension adjuster for the belt
tension)  The pivot bolt behind the timing belt cover is also a weak point
on this particular VW alternator mounting system...
  It is quite handy to adjust the belt tension.  What I've done is to
install a larger washer to spread the load on the hex bolt that meshes
into the rack of gear teeth..And I have now a spare arm for if mine breaks
(again)
  Don Hanson