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

Bob Brown blkbt7 at yahoo.com
Tue Jan 10 15:01:43 MST 2012


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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