Ignition coil summary

I find some of the older tech manuals fascinating. Many go into deeper discussions of various systems then I see in modern manuals. Some of my best are from the early 1900s.

That said - here is a great discussion of ignition coils from 1959. Including those "non existent" coils with internal resistors.

Considering farm tractors just about always used automotive systems - good reading to those types of people that like tech stuff.

Good post John, you're on a roll today, great postings yayyyyyyyyyyyy.

GREAT READING I FOR ONE APPRECIATE IT thanks for your time and effort in providing good information !!!!!!!!!!

INDEED as your posted literature shows, they made some coils (older autos perhaps??) that had an internal discrete stand alone resistor tucked away inside the can. Some had like a ring around the cans exterior where there was a separated compartment inside to house the resistor. However as a past used tractor dealer and farmer and having worked on literally HUNDREDS of various makes n models of old FARM TRACTORS I NEVER NEVER ran across any such coils on them. They (or at least the hundreds and different brands I owned and repaired) did NOT have any internal stand alone discrete "ballast resistor"

Of course NEVER SAY NEVER and there may have been an old FARM TRACTOR out there with a coil containing an internal resistor BUT I never ran across any. The farm tractor coils I observed (to my best knowledge and recalled memory NO WARRANTY LOL) and used DID NOT have coils with internal stand alone discrete "ballast resistors"

SURE SOME MAY HAVE EXISTED I don't have proof or disproof otherwise. Can anyone here help us out??? Perhaps someone has a detailed spec sheet of some old "FARM TRACTOR" that used a coil having an internal ballast resistor IF SO PLEASE POST so we can all learn something !!!

Best wishes, God Bless and Happy Easter

John T

PS I also saved the picture file you once posted that described how the wrong sized condenser causes pitting and/or mounding on opposite sides of ignition contact points. Ive read about it and was aware of all that, but didn't have that picture in my archives

Thanks again

John T

Thanks for posting that. Ron MN

not too many farmers have voltmeters and ask if their tractor is positive or negative ground. or dont know which wire goes where on the coil.
negative ground 12 or 6 volt system the coil negative goes to points.
positive ground 12 or 6 volt system the coil positive goes to points.
also when unsure of + or - ground looking at coil works too . so does looking at batt. cables but lots of time they gone or who knows how the guy had them connected.

It is important to remember that General Motors, Ford and Chrysler used different coils with different value resistors to match their respective coils. I recently measured the value of a new John Deere resistor and it measured 2 ohms. This closely matches a GM resistor which is 1.85 ohms. The point is, don't replace your tractors coil with one from an old car or truck sitting in the fence row without doing some investigation. These so called 6 volt coils used on 12 volt applications are different and need to be matched with the correct value resistor.