Odometer quit, 89 100 - lessons learned

[Dave C]

The repaired odometer is installed and working   Remember, this is the
electronic version (no speedometer cable) in an 89 100.  Here's what I
learned.
1. The speedometer needle must be removed to access the innards of this
thing.


2. Contrary to what many people say, this needle cannot simply be pried off.
The plastic needle is fused onto the shaft.  I was able to remove it by
first gently prying off the black placstic cap on top of the needle.  Then
heating the end of the shaft with a soldering iron and gently lifting off
the needle.  Replacement is the reverse... heat the shaft and gently push
the needle back on.



Apparently there are earlier designs where the needle >could< simply be
pried off.  I don't know when that changed.



3. I recommend obtaining a spare speedometer assembly before beginning the
repair because quite likely you will damage or break something.  The easiest
thing may be to just obtain a spare instrument cluster.



4. Odometer failure mode... there is a tiny gear, about 7 mm diameter,
inside the electric portion of the odometer.  This gear turns to mush over
time.  I'm not sure why but one thing I read is that the plastic reacts with
the lubricant used at the factory.  This would seem to argue against the
idea of fixing the odometer by simply replacing it with a used one of
similar age.



5.  The replacement gear you need is shown here ...
http://www.carradio.com/speedometer_gears.html labeled as VOLVO, AUDI,

MERCEDES BENZ (MB), PORSCHE 15 TOOTH GEAR #10-013 $28.00



6.  Be careful not to heat the speedometer shaft any more than necessary.  I
apparently ruined one speedometer with too much heat... it no longer rotates
freely.


7.  The speedometer face is delicate.   If the hot soldering iron gets too
close it can be damaged without even touching it.
- -
Dave C.