[Healeys] Fw: Possible explanation on the Petronix positive ground and Smith loop style Tach

Charlie Frazer cfrazer at jcomm.uoregon.edu
Tue Jan 10 19:19:16 MST 2012


This is an odd issue.
I've known a number of people (myself included) who run positive  
ground Healeys and Pertronix ignition with no special tach rebuilds.
Charlie

On Jan 10, 2012, at 2:01 PM, Bob Brown wrote:

A club member recently installed a Petronix ignition in his positive  
ground
BJ8,
Car fine s fine but the tachometer does not operate.  This is of course
because
it is not connected.


Several attempts to wire to operate the tach
ahve proven unsuccessful. He has
talked with Petronix tech support but they
could not provide a definitive
answer. I'm sure there are many positive
ground BJ8's in the owrld that have
properly functioning tachometers.  What
is the wiring??


Our club member sent me the following, which he now
believes to be his best and
possibly only option. I'm sure Niosonger knows
more about this than I do but I
have never heard that a paoistive ground BJ8
tach will not work unless rebuilt
as they state. A fair amount of cash has
recently gone into this car and I hate
to see him spend more needlessly.

Any
comments?

Bob


"I spoke to the owner at Nisonger Instruments.  They rebuild
the Smith
gagues...Anyway...I mentioned I was going to sen him my tach and
speedo for
rebuilding this winter...he casually asked about if I had
converted to
electronic distributor...and the truth came out.   The Petronix
he says is not
compatible with the loop tach style Smith gauge.  So they can
rebuild the
tach...to look authentic, but add electronics.  See link below.
He said they
rebuild a few hundred a year like this.  Not sure why it is not
common
knowledge.

So as you saw with my car...if you wire the coil and
distributor as Petronix
instructs...it works fine...you do have to remove the
wires from the harness
that used to terminate at the coil.  But apparently
you no amount of tweaking
will get the old tach to work."

http://www.nisonger.com/electric-tachometer-conversions.htm
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