Larry,
The earlier tach's round connectors (male and female) connect to an internal
loop - the white wires are connected internally via this loop (in fact, the
wires have male and female connectors to allow them to be plugged together
outside the tach if the instrument is removed - otherwise the car won't
run). The paired green wires are 12V switched power.
The later tach does not use a loop, the single round female Lucas connector
is connected to the points (negative) side of the coil, and the square 1/4"
male connector is for 12V switched power (your green wires). The case must
be grounded, either through the male connector or from a pigtail connected
under one of the instrument mounting nuts.
To hook up the white wires to your tach, first connect them together, then
splice off those wires with a single wire to the round female connector on
the tach.
Hope this helps,
Paul Kile
-----Original Message-----
From: Larry Hoy [mailto:larryhoy@prodigy.net]
Sent: Saturday, October 21, 2000 1:47 PM
To: MG V8 List
Subject: Tach conversion
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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