How to check coil

Typical resistances may show around 0.25 to 1.0 ohms in the low voltage primary (between ground and points lead) and maybe 5000 to 10000 ohms in the high voltage secondary (between ground and high voltage output terminal)

If the primary is open (infinite resistance) shes bad, and likewise, an open secondary means shes bad.

If the primary always reads 0 ohms (this depends on how good n accurate the meter is of course) I would wonder if its still wired to the points cuz either them or their wires or the condensor may be shorted n killing the spark. Make the reading with the coils primary disconnected form any points or condensor or kill wires etc to be accurate. An ohm meter on the points terminal with the coil connected ought to read in the 0.025 to 1 ohm range to ground with points open but 0 when they are closed. If she always reads zero remove the condensor and see if that cures the problem meaning the condensor or its wires are shorted. Ive seen points springs or wires or kill wires or consdensors or their wiring shorted which kills the spark.

Of course, the points have to be gapped proper and not burned up and fully open n close PLUS if its like most tractor mags, there needs to be a working impulse spring wind n trip assembly to produce a spark at the low cranking speeds.

Ol John T in Indiana

A coil tester "rings" them with an AC current.

Your meter probably isn't accurate enough at low ohms to get an accurate reading on the primary winding, as it will definitely have a measurable resistance, however, the coil secondary resistance is likely between 8000 and 16,000 Ohms between the high tension terminal and ground.

So, you CAN read the resistance of each winding, to ground.

The primary is wound with a relatively few turns of fairly heavy wire, so it's resistance will be low.

The secondary is wound with thousands of turns of tiny wire, so it's resistance is a LOT higher.

If you post what mag you're working with, someone will probably have a figure for the winding resistance. (It never hurts to close us in as to what you're working with!)

You say "I'm confused. My secondary reads 0 which sound reasonable if there is no electrical between the 2 seperate windings."

A reading of "0" would mean a dead short. Is that correct, or is the ohmmeter actually reading "infinity", meaning the winding is "open"?

What I am trying to do is not spend the $70.00 my local Kohler place wants for a coil especially since I can get by with that battery and coil for a while. Napa has coils for $37.00 so I ordered one and it is wrong, square hole in middle too large. I have 2 coils from a tecumseh that look identical to the coil in that Kohler. Those are the coils I am trying to test. I can get a new Tecumseh coil for $22.00 but don't know if it will work. To me is should but as I said my electrical knowledge is low. Should that Tecumseh coil work? Wish I had a known good one I could try.

I hope this isn't too off topic for this tools group but my original question was how to use the ohm meter, a tool, to test a coil and it has turned into this.
L.D.

Just cuz the points n condensor will make a battery powered external coil fire is no guarantee they will make a magneto coil fire due the the relative low energy in a mag versus what the battery can supply to an external coil. They can be marginal and still fire a battery powered coil but thave to be pretty well dead right to fire a mag coil.

Just hook one up n try it is about all you can do and so long as the air gap and physical location of the coil to magnet pick up is right she can still work REGARDLESS of brand etc.

John T Nordhoff in Indiana