[Healeys] Pertronix wiring

[Bob Spidell]

Sent to a Lister, passing on to the List:

The white/black wire from the coil to the Trusty Cutoff Switch 
(TCS)--yeah, I was being sarcastic because I know they can be 
problematic--is not even necessary in a standard points setup.  It only 
provides an alternative path to ground through the TCS so that when the 
TCS is in the off/don't run position the coil is constantly grounded and 
cannot produce a spark.  A coil--which is in effect a transformer--will 
only produce a spark when the current flow though the coil is 
interrupted; hence 'breaker points' (or, as in the case of Pertronix or 
other electronic ignition, 'breakerless').   A Pertronix 'breaks' the 
circuit upstream of the points, but it still requires a path to ground 
so the current can flow when the transistor is on; the white/black wire 
from the coil can provide a convenient path to ground and retain the 
'theft preventative' aspect of the TCS.

In a standard points setup, the TCS breaks the connection from the 
battery to ground in the OFF position, rendering the starter and all 
other electrical components inoperative, but it also connects the coil 
to ground, rendering the coil unable to produce a spark since the path 
to ground cannot be broken.  The Pertronix requires a separate path to 
ground, and the white/black wire can be used for this since, yep, it's 
already a patch to ground.  I'm working from memory--my car is at my 
folks'--but I think all you have to do is move the white/black wire on 
the TCS to the same terminal--the large one--that connects the battery 
to ground (but it's a larger terminal by necessity so you'll need to put 
a larger terminal on the wire).   Then, not only will the battery be 
disconnected from ground in the OFF position, but the coil will be too.

On the points setup, you have 3 wires on the coil: one from the current 
source--the ignition switch--and 2 to ground; one path is through the 
points, and the other--the white/black--to the TCS. With the Pertronix 
setup you only need 2 wires: one from the Pertronix output and one to 
ground (see the schematic on the Pertronix site for which Kees provided 
a link).  The white/black wire is already there; why not use it?

On a positive ground car, you want the 'SW' or '-' terminal to be wired 
to the source of the current; in a points setup this is a direct 
connection to the ignition switch (hence 'SW'), but in a Pertronix setup 
it will be the output from the Pertronix.  The 'CB' (Circuit Breaker == 
points) or '+' will be a path to ground, either through the points or 
through a separate, 'dedicated' wire, of which the white/black wire is 
ideal.  Note if the terminal is marked with '-' and '+' it's intuitive 
that the '+' should go to ground, one way or another.

One weakness in the original Pertronix is if the unit is forward 
biased--i.e. 'on'--current will flow continuously and the unit will get 
fried in a couple minutes.  So, never leave your ignition switch in the 
'run' position when the engine isn't running; with a points system you 
could fry your coil, with Pertronix you might fry both the coil AND the 
Pertronix.

Note the car should run with the coil connected backwards, but I won't 
produce as strong a spark.


On 12/20/2016 8:32 AM, Bob Spidell wrote:
>
> re: "... I don't think a connection between the coil and chassies is a 
> good idea ..."
>
>