JD 60, 12 volt coil getting hot

[JLevault]

I have been tinkering with getting my grandpas '56 model 60 running for a while. One thing I did was replace the coil because it did not ohm as it should, it is now less 2 years old. I also swapped the dual 6v batteries, run is series I believe?, for a single 12v. I know for sure it is a 12 volt system.

My question is why does the coil get hot to the touch when running? I have never noticed it to be hot before. Should i go back to the two battery system? Can anyone explain why the two batteries instead of one originally?

 

[John T]

JL, 12 volts is still 12 volts REGARDLESS if its two sixes in series or a single 12 volt so that shouldn't affect coil
current and heat. Way back then two sixes were used (to get adequate voltage and CCA rating) but nowadays most everyone
replaces with a single 12 volt NO PROBLEM.

NO you DO NOT have to go back to two batteries, I prefer a single 12

COIL HEAT

Ifffffff its a 6 volt coil on a 12 volt system with no external series voltage dropping (12 down to 6) ballast resistor it
will overheat badly plus burn the points premature.

On a 12 volt tractor you can use EITHER a full true 12 volt rated coil orrrrrrrrr a 6 volt coil PLUS an external series
voltage dropping (12 down to 6) ballast resistor.

A full true 12 volt coil may be labeled 12 Volts or 12 Volts no ballast required and will have a LV primary resistance
of around 2.5 to under 4 ohms, many around 3 ohms

HOWEVER a Coil labeled 12 Volts for use with ballast is in reality more like a 6 volt and needs the ballast as it says or
it will overheat.

A 6 volt coil will have a LV primary resistance of around 1.2 to 2 ohms (many 1.5) and if used on a 12 volt tractor without
a ballast it will overheat...

SOOOOOOO is it a 12 volt or a 6 volt coil ????? What is its LV primary resistance ???

Other causes of overheating may be where the coil is mounted (too close to exh manifold etc),,,,,,,,,or how well or where
any metal mounting strap and clamp are located to dissipate heat away from the coil,,,,,,,,,,or excess voltage

John T

 

[wore out]

"One thing I did was replace the coil because it did not ohm as it should"

Was it running with the old coil?

What Ohm readings did you get from the old coil that you assumed were "not as they should be"

If I remember correctly, originally there would have been a primary resistor at the ignition switch, allowing what was basically a 6 Volt coil to be used.

If a P.O. changed the wiring and eliminated the primary.ballast resistor you will need to use a "true" 12 Volt coil that operates on 12 Volts with no external resistor required.

Any numbers on the old coil, and what is the part number of the new coil?

 

[old]

It is the very nature of electrical thing to get warm/hot so good chance it is normal.

As for 2 6 volt batteries or 1 12 volt the coil doesn't know the difference 12 volts is 12 volts period

 

[rustred]

definitly not normal for the coil to get hot, and i know that. John T the engineer gave to results and you still posted its normal.

 

[old]

Every coil I have had got warm enough I sure will not stand there and hold on to it. Now if it is so hot if you spit on it and it steams off fast that is to hot. But again as asked please just leave me alone since we will not get along or agree with each other since no matter what I say you think I am wrong

 

[rustred]

well what is it, warm or hot? two different things. totally normal to be warm, to be hot that you cant hold it is not normal. and if its that hot that your spit is steaming off of it then i am sure the tractor wont be running due to that. i will keep on replying with correct answers too, not stuff you pull out of the rafters.

 

[Kalven]

Is the tractor still positive ground or
been changed to negative ground? The coil
needs to be hooked up according to the
ground. If not it will get hot.

 

[JLevault]

(quoted from post at 15:20:52 04/13/21) Is the tractor still positive ground or
been changed to negative ground? The coil
needs to be hooked up according to the
ground. If not it will get hot.

Thanks for all the replies gents. This weekend I will have time to gather part numbers and test the coils again. and make sure it does or does not have a resistor. I have the old one still.

The tractor is still positive ground, very certain I hooked the coil up that way but I will check it.

again, thanks! I dont want an electrical fire in my shed over a wire swap.

 

[wore out]

"The coil needs to be hooked up according to the
ground. If not it will get hot."

NO, it won't.

But spark effectiveness under certain conditions will be less/weaker if it is connected backwards. (Misfire under a heavy load MIGHT be a symptom.)

If the ignition system is producing a hot/decent spark swapping the polarity won't make a noticeable difference.

Many modern cars have used a "waste spark" system where one coil fires two sparkplugs, one at the more desired polarity and the other polarity and they work just fine because the spark is so "HOT" it fires both plugs under load with no issues/misfires.

 

[John T]

Thanks for the feedback, its not all that hard to verify the coil voltage plus the necessity (or not) of any ballast and wire
it at the correct polarity.

John T