6v Coil - Pos or Neg Ground?

[Jose Gomez]

So pre WW2 in the USA all coils were marked + and - and everyone knew that - went to the distributor?   

When the + ground and 12V stuff came out were those coils clearly marked as such or was it just a manufacturer part number? 

TJ,

I have to correct my previous comment for the positive ground coil setup; once again I was deriving my comments base on the negative ground, my apologies.

For a 6V OEM type the best option would be to test the resistance, and not to rely on the markings. From the high voltage output socket to each connector, the one with the least resistance would be the one going to the ignition switch side.

Here are the wiring instructions for a 6V positive ground coil from Petronix.

http://pertronix.com/support/manuals/pdf/ignitor6vpos.pdf

[Wayne Womble 12210]

You had better have a pretty dog gone good Ohm meter.  Measuring 10,000 vs 10,001 ohm is impossible on most normal shop meters. 

The diagram shown for the Igniter is not typical of points wiring.  So I am not sure that says much for how it should be wired. 

[Classic]

I notice in the Pertronix instructions that Jose posted that it says to connect a 20 gauge wire from the positive coil terminal to the chassis (for a positive ground car).  20 gauge may be adequate electrically, but not mechanically.  Given the harsh conditions in an engine compartment (heat, vibration, potential for mechanical damage), a minimum of a 16 gauge wire should be used and be taped or tie-strapped to other harnesses.  A 16 gauge wire has a heavier conductor as well as  heavier insulation.  I'm a retired OEM electrical engineer and this is what my company did.

[Jose Gomez]

You had better have a pretty dog gone good Ohm meter.  Measuring 10,000 vs 10,001 ohm is impossible on most normal shop meters. 

The diagram shown for the Igniter is not typical of points wiring.  So I am not sure that says much for how it should be wired. 

Wayne,

Sorry for the confusion and the many intricacies around this topic.

The safe assumption for a positive ground system will be (if the coil is an OEM or equivalent replacement and there are no instructions) to follow the polarity stencil on the coil with the car polarity that is Ignition switch (which is negative side) = negative of coil, breaker points (which is positive ground) =positive of coil, this way both will match.