aha...now that is a good idea.  somebody will correct me if i am wrong
on this.  but the rapid switching of a maybe six to twelve volt source
looks likely. by the time the tach sees the signal voltage i believe it
will be in that range.
there is a trick to the tachs though.  the tach on my 84 jetta was
almost a straight shot of the coil but  the tach in my  91 jetta got
its signal through a circuit on the back of the dash.  when i fed it
signal from the coil it just sat there leading me to believe the tack
was actually integrated into the vehicle circuitry for the computer to
analog conversion stuff.
i think i will play with that tomorrow with one of my tach meters.
jimt
On Thursday, Oct 17, 2002, at 12:22 America/Denver, Leon Korkin wrote:

> David and other listees who helped re:tach,
> Thanks!
> Let me clarify the purpose of why i asked
> I know that some Rabbit or Golf tachs will work in Vanagon, got one
> of those myself working in my Westy.
> Still don't know exactly which work and which don't.
> Most look exactly the same. Just got tired of buying them
> at Pick-A-Part and finding they don't work. It's a bit of work
> retrieving one from car. So, just wanted to check on the spot
> if i am getting good one, hence my need for a tester.
> Thanks
> Leon
> 85 Subwagen Westy
>