Group,

I want to test or run a speedometer on a workbench.  I am not trying
to calibrate or test any thing other than the fact that the
speedometer drive operates and the odometer gearing is in tack.  I can
assume that the speedo drive is powered by a signal that originates at
the tail shaft sensor but I can't find what the end electrical product
is at the speedometer.  Would it be possible to use a signal generator
and stimulate the drive in the speedometer to turn?  If so dose any
one have specific knowledge about what frequency and shape the signal
should be and what voltage and current involved?  Also is a primary
power source required at what connections?  I know repair shops bench
test these units.  I have several of these 126 chassis VDO units that
need tested and I feel there is a way but need help to get started.
These speedos are all from the 126 and 107 Mercedes (alike)

Thanks Bruce Buchanan,