If so, chances are you have a very common problem with VW odometers. Look for a detailed writeup on this fix on "Jan's VW page". There are detailed instructions on the fix there.
In my case, the fix was easier than described above, it was simply the main spur gear that is driven by the worm gear that had cracked. It is a press-fit nylon gear on a 3mm shaft. As the worm teeth passed the crack, the crack would expand, allowing the worm gear to slip past the spur tooth (i.e. click!). I pulled the spur gear, reamed out the hole to 1/8" (a shade over 3mm) then used some activated super glue to glue the gear back onto the shaft. With the larger hole, stress of the press fit is relieved allowing the crack to remain closed and the glue now holds the gear to the shaft instead of the press fit (which led to the crack in the first place).
$3 for some plastic-compatible super glue
-- (it depends on how hard you need to work to get to the odometer)