Speedometer works, odometer doesn't....

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Marie - 02 Dec 2003 03:28 GMT

Just noticed the odometer (including trip odo) in my 1991 Spider has
stopped working, however the speedometer itself is working just fine.
Any ideas as to why and what it will take to fix it? Thanks.

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Dev Cloete - 02 Dec 2003 21:51 GMT

The odometer is driven by a small steppermotor which is driven in turn by a
small integrated circuit inside the speedo. If the instrument is opened the
pulse from the gearbox can be similated by a 6Volt square wave from a signal
generator or by the speed sensor itself removed from the gearbox. You can
then observe whether the steppermotor is running or not. The chances are
good that the plastic gears or wormdrive from the steppermotor is worn or
not meshing propperly as the electronics are quite robust.
Good luck

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Gordon - 04 Dec 2003 10:49 GMT

I may be worng, but to my knowledge the speedo and the odometer are
driven by the same steppermotor. Since the speedo works fine according
to post, there should be no need for testing with pulse generators...

My bet's on the plastic stuff; should also be apparent by a ticking
sound coming from the odometer. If there's no ticking sound, chances
are something broke off completely or one of the axles has run out of
it's bushings.

>The odometer is driven by a small steppermotor which is driven in turn by a
>small integrated circuit inside the speedo. If the instrument is opened the
[quoted text clipped - 4 lines]
>not meshing propperly as the electronics are quite robust.
>Good luck

Gordon

Giulietta 1.8 '82
GT Junior 2.0 '75
GT Junior 2.0 '74 (project)

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