The white wires on your old tach create a loop inside the tach working as the
very early models that
had an external loop. These wire need to be joined as they create the feed from
ignition to the plus
side of the coil.
A new wire must be run from the negative side of the coil to the male terminal
on your new tach. The
new tach needs power to the other insulated terminal. This can be the original
2 green wires from the
original tach.
The remaining uninsulated terminal is case ground, to any convenient spot.
Jim Stuart
Larry Hoy wrote:
> I have a question about the tach conversion using the 100k potentiometer
>(pot).
>
> My 1969 car came with the earlier style tach. Apparently this tach is not
>suited for the mods as
> outlined in the MGB V8 newsletter, and Leon Zaks web site. I scrounged up
>another suitable tach
> from my stash and made the mods.
>
> When I went to install my newly modified tach I found there is a wiring
>difference in the two tachs
> and my car doesn't just "plug in" to the new tach.
>
> The old tach electrical connections consist of a:
>
> round female Lucas connector (had a white wire attached that goes to the coil)
>
> round male Lucas connector (had a white wire attached that goes to the ign
>switch)
>
> male 1/4" connector (had two green wires attached dunno where they go)
>
> The new tach has a:
>
> round female Lucas connector
>
> a square 1/4" male connector.
>
> male 1/4" connector on the case for ground.
>
> Notice there is one less connector.
>
> Can anyone help me with this dilemma? What wires go where?
>
> Larry Hoy
> Still sorting out the odds 'n ends
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