Coil Polarity?

stallerl

stallerl

Senior Member
The coil on my '29 does not have any + or - markings on it. Does it matter how the two wires are connected to the coil? :confused:
 
stallerl said:
The coil on my '29 does not have any + or - markings on it. Does it matter how the two wires are connected to the coil? :confused:
Click to expand...


Most of the suppliers sell a device that you temporarily plug into the top of the distributor. It has two LED's along the side. When you fire the engine up one of the LED's will flash indicating correct polarity or reversed. It is a nice thing to have to be able to get the coil polarity correct, despite what is or is not marked on the coil.

A number of years ago when they first came out I purchased one and at a club function we tested about 20 Model A's and about half were reversed and the owners had no indication. A reversal robs only a few horsepower.

It is easy enough to correct, just swap the two primary wires at the coil.

The pencil test shown in the link on the second post was a favorite of my 9th grade auto shop teacher. He would demonstrate to the class and them have members of the class try it and then quietly watch as they got knocked on their butt.

Tom Endy
 
Thank you all. So the engine should start and run even with the two primary wires crossed, although with a weaker spark correct?
Tom, Do you know if the OCMAFC has a tester I can borrow?
Thanks again!
 
I don't like getting shocked, especially with a flame thrower coil!! Snyders lists the polarity tester on page A-148 of the new catalog, part number A-12116 . It lists for $23.95 . In some cases this is more expensive than a replacement coil but in my opinion is worth the price. With this tool you will know for sure if the coil polarity is correct. although the model A will run either way, it does make a noticeable difference when the coil polarity is correct.
 
stallerl said:
Thank you all. So the engine should start and run even with the two primary wires crossed, although with a weaker spark correct?
Tom, Do you know if the OCMAFC has a tester I can borrow?
Thanks again!
Click to expand...

I have one that you can borrow if you like. Trouble is, that I am a few miles from you. San Fer. Valley. I would think some one in your area would have one.
 
tams has them for 22.50
it can also be used as a spark tester for driveability problems...
worthwhile small investment to have
 
stallerl said:
Thank you all. So the engine should start and run even with the two primary wires crossed, although with a weaker spark correct?
Tom, Do you know if the OCMAFC has a tester I can borrow?
Thanks again!
Click to expand...

I have a tester. There is a club seminar scheduled at my house on July 20. Bring your car and I can test the coil polarity for you. I am in the club roster.

Your car will run just fine with the polarity reversed. A little better when correct.

Tom Endy
 
I am hoping I will have the car on the road by the 20th and if I do I will certainly bring the car to the seminar.
Thanks Tom,
Lou
 
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