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Re: Help With Tachometer

To: Jan Eyerman <jan.eyerman@usa.net>
Subject: Re: Help With Tachometer
From: Jarrid Gross <jarrid_gross@earthlink.net>
Date: Sat, 31 Jan 2004 21:00:44 -0800
Jan Eyerman wrote:
> 
> I just bought an Alpine IV positive ground tach for my '62 Hillman Minx.  How
> is it wired?  Where does the connection on the Lucar (push on type) connector
> go and where does the odd little screw on connector go?

Its been a while since Ive been behind the lucas tach, but
there should be 3 terminals on the back of the tach.
1) Is the tach power.
2) is the ignition switch connection.
3) is the coil feed.

Terminals 2 and 3 are the lucar, one will be a male, one a female.
I suspect the threaded one would be the tach powwer connection.

On the lucar terminals, one of the two terminals goes to the battery
side of the coil+ballast, the other connector goes to the ignition
switch (ignition on position).
The tach power connection also goes to the ignition switch (ign on
position).

The tach leads forms a current loop, that passes the ignition coil
current
into a transformer internal to the coil.

If you measure the resistance between the two lucar leads, you will
measure
less than an ohm (essentially a short).

Lastly, the case of the tach serves as the ground (-12v) so make sure
you
have the tach case tied into the "daisy chain" of ground connections.

See WSM124 Section N Page 40 for the schematic.

HTH

Jarrid Gross





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