12 Volt coil

I have a john deere 4010 propane tractor. I am having a problem with the coil getting hot and damaging the coil. What would be causing this.

most likely got the wrong one 2 types are avaliable one requires an external resistor the other has an internal resistor either one will work as long as a resistor is used with the coil that requires one

in addition to my last post didn't jd use 24 volts to start some of the early 40 series tractors if so you could have a problem with a resistor or other component in the ign system causing the coil to receive 24 volts instead of 12 volts

Oh no the dreaded John Deere 24 volt mentioned. Yes they used 24 volts to start but if I understand everything that has been written about them here they're not really a 24 volt system, it's more like two 12-volt systems that gang up to run the starter, and only the starter, on 24 volts. Lights ignition, gauges, cigarette lighter and heating/cooling (if equipped with a cab) all run 12 volts.

24 volt starting was only on diesels as far as I know.

Well if it is a 12 volt system you may have the wrong type coil or the coil need a ballast resister in line with it. A coil will say on it no resister needed or resister needed or some such thing that means the same thing.

(quoted from post at 22:52:17 05/21/12) 24 volt starting was only on diesels as far as I know.

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ou are right.........never ceases to amaze me at all the mis info people introduce into these threads! :roll:
not helpful at all.........just more smoke.

Your are talking pure and total bull sh!t .

Points are designed to operate with 4-5 amperes of current (at least that's what the manuals say that I read; I don't design conventional ignitions).

For a 12v battery, 5 amperes is 12.75 or lets say 13.5volts if your gen is working, divided by 5 amperes = 2.7 ohms.

When the points are closed, with the proper dc resistance (the thing you read with a multimeter on ohms scale and the engine not running), normal current flows through the primary of the ignition coil for the duration of the charging cycle (dwell). The points open and the energy now stored in the coil is released into the spark plug....bang!

Soo, depending on the dwell time, number of cylinders, rpm and all, Ohms law says that the coil resistance x the current flow (squared) flowing through it will generate heat in the coil; the normal process with a little additional heat added from the fact that they are usually conveniently attached to the side of the engine block.

Soooo if you have no/too small a ballast resistor to limit the current, you can over "wattage" your coil and it can be destroyed from heat, along with your points burning up prematurely from the over current/over sparking that your "condenser" may not catch due to the excessive energy stored in the coil [w (in watt-seconds) = 1/2 L (inductance of the primary winding) x I (dc current flowing through it when the points open) squared].

I know you didn't ask for that but if I don't use it from time to time I will forget it.

Sooooooooo you might get out your ohmmeter on the OHMS, 20 is a popular number with DVM's for the scale, and measure from the cold side of your ignition switch (switch off) to the black wire that goes into the side of your distributor. If you measure too few ohms, you have found your smoking gun.

Mark

(quoted from post at 10:20:15 05/22/12) Your are talking pure and total bull sh!t .

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Who are you directing this at?

There are no coils with an internal resistor in them.There no room plus a hot 40 watt resistor would overheat the coil.Heres where the internal resistor fable comes from.Dufus reads a lable on the coil or the box that says No resistor required.So he thinks theres one inside the coil itself.He dosent know that tranformers are wound to match the voltage they run at.Ford used a resistor in series with the ignition coil 1933 to 1948.It was under the dash until it was moved to the ignition coil in 1948.