RE: '84 5kS odo/speedometer...

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

> Here's a good one: Speedometer works,
> std. and trip mile counters are stuck.
> Since the way to defraud a buyer would be 
> to run without the main counter counting, and then 
> attach it before selling, one should assume
> that it's an honest defect, no?
> 
> More importantly, am I correct in assuming that both run
> off the same cable, and the 'open fault' is in the
> cluster itself?
> 
Yup ... this is actually a pretty common malady ... I've dealt with it both
on the '78 Audi Fox and the '83 QTC.  So far the '85 4kQ is working ... and
at over 200K miles it makes one think that VDO may have figured out how to
build them better somewhere between '83 and '85.  The newer cars ('87-88
5kCSQ, '91 V8Q) do away with the speedo cable, and electronically couple the
speed signal to the speedo/odo ... which provide an entirely different set
of problems ...

The problem is actually within the speedo itself and may be one of several
possible sources.  First, there is a plastic gear that couples the worm gear
that is driven by the speedo to the main shaft of the odometer.  A plastic
gear with a shaft press fit in the center is prone to breakage ... and that
is what happened to mine on the QTC.  Once the gear breaks it is difficult
to actually couple the motion to the odo shaft.  My symptoms were that the
odo would work for a short time when the car was cold, but as the car warmed
up and the odo ran over some number of 9's it would stop.  Others have
reported slipping of this gear even without it actually breaking.  The next
possibility is that the odometer wheel that couples the rotation of the main
shaft to the odometer itself has come loose.  Once again we are talking
about a press fit situation.  You can take the Instrument Cluster out and
take it to a VDO repair facility, where they will repair it for you for
around $60, or you can fix it yourself for next to nothing ... as long as
you don't need to replace that plastic gear it is only a matter of
increasing the coefficient of friction between the shaft and the two "gears"

HTH!
Steve Buchholz
San Jose, CA (USA)