Changing the Ignition Coil

[Ed in Maine]

I should have paid attention to the connections on the coil before I took it off the car. The old and new coils do not have the spot welded bracket.
The coil is screwed tightly to the bracket. The new coil is marked Positive (+) and Negative (-). Which terminal on the coil should the red wire coming from the ignition switch out of the terminal box be connected to on the coil? Thanks for your help, Ed

[Rob Doe]

Ed, if your car is a 6 volt, positive + ground at the battery to frame connection, then the red wire to the switch and on to the points is attached to the + positive side of the coil.

[nkaminar]

There is a tool available to make sure you have the polarity right. See https://www.snydersantiqueauto.com/p...6303&cat=41753. Snyders is out of stock today. Check with the other vendors.

[eagle]

As was said above, if car is stock + to distributor.

[Tom Endy]

The attached article may help.

https://www.santaanitaas.org/wp-cont...pful-Tools.pdf

Tom Endy

[nkaminar]

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Actually, the coil does not care which polarity it has, it is the spark plug that cares. The electrons will jump easier from the hot center electrode than the colder grounded electrode. Once the initial jump occurs the air is ionized and the electron flow is easier. That enables the multiple jumps going in opposite directions as the coil/condensor system rings. The ignition system is more complicated than most people realize. The devil is in the details.

Lightening works the same way. You have probably seen this. Once the air is ionized multiple discharges of the static electricity can occur, causing multiple flashes along the same path as the initial discharge.

[Ed in Maine]

Thank you for your answers, Ed

[Y-Blockhead]

You can check your coil polarity with a analog volt meter.

1. Connect the negative lead to the coil secondary terminal and the positive lead to the engine block.
2. Set the meter on the highest volt range (these connections are the same whether you have a positive ground or negative ground electrical system).
3. Crank the engine over (do not start it) and the needle of the voltmeter should show an upward swing to the plus or positive side (don’t worry about taking a reading).
4. If the needle swings down to the negative side and gives a negative reading, your coil is hooked up backward. To correct the polarity, simply reverse the coil primary leads.

[Bob Bidonde]

This slide may help you.

[ModelA29]

Here is a pretty good article - https://mossmotoring.com/coil-polarity/

[ndnchf]

I just got a Pertronix 1.5 ohm epoxy filled coil. Before installing it on my '31 pickup, I made a short video testing it on my vintage Herbrand coil tester.

https://youtu.be/TfK88Jt3DrQ?si=XeTLjVWjrHHMe3LT

[Bruce of MN]

Maybe more info: https://www.chicagolandmgclub.com/te...neral/574.html

[Pete]

Originally Posted by nkaminar

Actually, the coil does not care which polarity it has, it is the spark plug that cares. The electrons will jump easier from the hot center electrode than the colder grounded electrode. Once the initial jump occurs the air is ionized and the electron flow is easier. That enables the multiple jumps going in opposite directions as the coil/condensor system rings. The ignition system is more complicated than most people realize. The devil is in the details.

Lightening works the same way. You have probably seen this. Once the air is ionized multiple discharges of the static electricity can occur, causing multiple flashes along the same path as the initial discharge.

Coils are designed to have the wire that starts next to the core in the primary winding as negative battery. That is usually the one marked "-" or minus.
They will work either way but this is most efficient.

For lightning, the leader bolt comes down and ionizes the path, The main bolt /charge goes up.