VW/VDO Odometer Repair
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Does your Odometer click every mile? 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 a fix there. Howeve, lets for the
sake of this discuussion, assume that the problem is with the main spur
gear that is driven by the worm gear that is cracked. It is a press-fit
nylon gear on a 3mm shaft, over time, the plastic fatigue and crack
from the press-fit. As the worm teeth passed the crack, the crack will
expand, allowing the worm gear to slip past the spur tooth (i.e.
click!). One might be tempted to pull the spur gear off the shaft, ream
out the hole to 1/8" (a shade over 3mm) to relieve the stress,
then used some activated/catalyzed 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).
You can see the steps involved in the images below. The speedometer can
be removed from the instrument cluster by removing the screws that hold
it in place. Then, remove the two screws that hold the back plastic
cover and look for the worm gear/spur gear combination that drives the
odometer. If the spur gear has a crack, that is the source of the
Broken odometer drive gear
1/8" drill bit to enlarge the 3mm press fit hole
Odometer gear reattached with plastic cyanoacrylic glue
Several points are key in this repair procedure:
The hole in the gear is reamed out to release the stress of the
A plastic-rated adhesive is used to glue the cracked gear back together
as well as to hold the gear to the shaft of the odometer.
It is fairly easy to remove the instrument cluster after removing the
dash panel, pressing the headlight switch release button, disconnecting
the speedometer cable and finally disconnecting the electical
connector. The the cluster may be tilted forward and removed. It is not
necessary to remove the steering wheel but doing so will give you more
room to work.
Since it seems to work for the Snake Oil Vendors, I
figured I might as well hype the MPG improvement of this fix. This
simple fix will gain you 5-10% (or more) MPG. Why you ask? The gear in
question has 20 teeth. It rotates once per mile. Every click is 1/20th
of a mile (or 5%). Mine seemed to click one or two times per mile, on
average, so I think you'll see a 5-10% MPG improvement (measured not actual).
Tampering with the odometer may have legal implications, so proceed
with caution, YMMV, yada-yada-yada...
Other folks have reported that wrapping a fine copper wire around the
hub of the gear along with some good epoxy glue can help to keep the
gear from re-splitting. Another option is to find a small washer that
can be press-fit over the gear hub and then glued in place. In any
even, both these techniques strengthen the gear to resist the force of
the press fit.
Some later model A2 and A3 vehicles may bave a metal drive gear instead of the plastic one. In this case, the likely cause of the problem is that the gear is slipping on the shaft. You can either try using an exopy glue to lock the gear in place, or try roughening up the shaft, after carefully pulling the gear off, and then carefully reinstall it or try shrinking the hub of the gear a bit with a small nail set punch around the circumference.
$3 for some plastic-compatible super glue
-- (it depends on how hard you need to work to get to the odometer)
Note, the stock VW odometer drive gear is 21 teeth, at least on the A1
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[Last updated: 03.May.2011]