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Deere uses the same coil on most 12 volt-system tractors as they do on 6 volt-system tractors. Thus the resistor. Your coil only gets full battery voltage when cranking (around 9-10 volts).
At that time, 12.7 volts at the battery naturally drops to 9 volts from cranking load. Once started and generator voltage rises to over 13 volts - the resistor drops it to 8-9 volts at the coil.
At that time, 12.7 volts at the battery naturally drops to 9 volts from cranking load. Once started and generator voltage rises to over 13 volts - the resistor drops it to 8-9 volts at the coil.
If you have a standard Pertonix electronic kit - it must be used with the original resistor and original coil - or a special "medium ohm" coil they sell. They claim that the original "6 volt" coil without the resistor can burn the unit out. Ohms on the primary are too low. That is for the standard "Ignitor" kit. The more expensive "Ignitor II" and Ignitor III" kits CAN be used with low ohm coils like have.
I don't understand the purpose of the question then.
The original resistor is needed with the original coil. If you used a Pertonix I kit it still needs the resistor with the original coil. If someone sold you a coil with higher ohms on the primary and said the resistor is no longer needed - then you don't have to use it (or you still can if you like). The purpose of the resistor is to protect the original points from burning out prematurely and to extend the life of the coil. The standard Pertonix kit is not as rugged as the original points and will burn out if run too long without the resistor IF the OEM coil is used. They sell their own coil that already has a higher resistance built into it so the extra external resistor is no longer necessary.
The original resistor is needed with the original coil. If you used a Pertonix I kit it still needs the resistor with the original coil. If someone sold you a coil with higher ohms on the primary and said the resistor is no longer needed - then you don't have to use it (or you still can if you like). The purpose of the resistor is to protect the original points from burning out prematurely and to extend the life of the coil. The standard Pertonix kit is not as rugged as the original points and will burn out if run too long without the resistor IF the OEM coil is used. They sell their own coil that already has a higher resistance built into it so the extra external resistor is no longer necessary.
OK, I actually found the paperwork. Its a Pertonix kit, and it came with a new coil. And looking at the instructions it says to remove the resistor.
I'll have to look and make sure I did that.
My original question is: (I have lots of trouble starting the tractor and am trying to eliminate problems) I'm measuring about 8-9 volts at the coil. Is that normal or is it low? And if the battery is supplying about 12.5 volts, what is dropping the voltage down?
I'll have to look and make sure I did that.
My original question is: (I have lots of trouble starting the tractor and am trying to eliminate problems) I'm measuring about 8-9 volts at the coil. Is that normal or is it low? And if the battery is supplying about 12.5 volts, what is dropping the voltage down?
All 12 volt starters are designed to work at 9 to 10 volts. 12 volts would be near impossible. It is normal with a properly sized battery to drop down to 9 or 9 1/2 volts when cranking because of the load put on it. A fully charged 12 volt battery is around 12.7 volts when it is NOT being used. Once you draw power out of it, the voltage drops. The more draw, the lower the voltage gets. If you put a huge oversized battery in your tractor, you might get it to crank at 10 volts.
For the same reason, "12 volt" ignition systems are also designed to work at 9-10 volts. The Pertronix starts giving trouble at 8 1/2- 8 3/4 volts. It is more touch with low voltage then when using ignition points. So, you need a good battery and also a good starter that is not drawing more then it should. Also keep in mind that when temps get down to 0 F, battery power is cut in half. So a tractor or car or truck used in cold regions is supposed to have twice the battery it needs in warm starting -so it can also start cold.
For the same reason, "12 volt" ignition systems are also designed to work at 9-10 volts. The Pertronix starts giving trouble at 8 1/2- 8 3/4 volts. It is more touch with low voltage then when using ignition points. So, you need a good battery and also a good starter that is not drawing more then it should. Also keep in mind that when temps get down to 0 F, battery power is cut in half. So a tractor or car or truck used in cold regions is supposed to have twice the battery it needs in warm starting -so it can also start cold.
Machinery-Man
Well-known Member
I put a bunch of these on 2 cylinders and it "always" called for removing the resistor or hooking to the 12v side. I always used the coil that came with the kit. Why buy trouble. My instructions were clear. Also it said never try to start by jumping as the unit requires a charged battery. They always worked great. I have not idea where the resistor is on the 3010, I suppose it could be in the switch. I don't know if they orginal used a jumper wire from the starter like the 2 cylinders to boost starting during cranking. I know you don't need any of this on electronic as the spark is super hot. You may have other problems. Iknow the old two cylinders would start even with wetting the coil and cap. Also they would start when even if you fouled the plugs. Great system...question your installation, especially since you can't find paperwork....
Bob, I got here late and pretty much agree with LJD, FWIW heres my take.....
YOUR QUESTION: What's the purpose of the resistor in the circuit that goes from the ignition swith to the coil?
ANSWER" Its purpose is to drop somewhere around 6 volts so the 6 volt coil only sees the 6 volts it was designed and engineered to handle OTHERWISE the coil could overheat and the points burn up prematurely due to excess current switching.........
YOUR QUESTION: I have about 12.8v at the battery, and 8-9v at the coil. Is that normal or is that low? ITS NOTTTTTTTT LOW
ANSWER: With the elec switch closed and conducting (like if points were closed) that number could be on the high end (Ive seen it from 6 to 7 + normally BUT it depends on the BATTERY VOLTAGE,,,,,,,, The ohms value of the ballast,,,,,,,,,,,And if its also a Thermistor (temp compensating) it may increase resistance once warmed up meaning the coil would then see even less voltage, maybe more in line with 6 to 7 volts, subject to temperature and ballast ohms and battery voltage well duhhhhhhhhhhh.
NOTE the coil must be matched (its ohms value) to the current rating of the elec switch or you could burn up the switch CHECK WITH PERTRONIX. Just because its an ELECTRONIC switch versus mechanical contact points doesnt mean you can pump a ton of current through it and you cant use it to switch more current then its rated for anddddddddddddddd its the ohms value of the coil (+ any series ballast) that determines how many amps the switch is handling.
Basically IFFFFFFFF Pertronix says KEEP THE BALLAST that tells me their switch isnt rated to handle all the extra current that would result if you used a 6 volt coil (which could also overheat due to excess current from a 12 volt battery) unballasted !!!!!!!! DO WHAT THEY SAY THEY KNOW THE SWITCH RATING NOT US GUYS HERE. Of course, if you bought a new 12 volt coil (NO ballast required) and its internal primary resistance is near what a 6 volt coil PLUS BALLAST is,,,,,,,, THEN THE CURRENT IS THE SAME AND NO BALLAST WOULD BE NEEDED
Hope this explains the theory and answers your questions NOW CHECK WITH PERTRONIX SO THE COIL PLUS ANY BALLAST DOESNT EXCEED THE SWITCHES RATING
John T
YOUR QUESTION: What's the purpose of the resistor in the circuit that goes from the ignition swith to the coil?
ANSWER" Its purpose is to drop somewhere around 6 volts so the 6 volt coil only sees the 6 volts it was designed and engineered to handle OTHERWISE the coil could overheat and the points burn up prematurely due to excess current switching.........
YOUR QUESTION: I have about 12.8v at the battery, and 8-9v at the coil. Is that normal or is that low? ITS NOTTTTTTTT LOW
ANSWER: With the elec switch closed and conducting (like if points were closed) that number could be on the high end (Ive seen it from 6 to 7 + normally BUT it depends on the BATTERY VOLTAGE,,,,,,,, The ohms value of the ballast,,,,,,,,,,,And if its also a Thermistor (temp compensating) it may increase resistance once warmed up meaning the coil would then see even less voltage, maybe more in line with 6 to 7 volts, subject to temperature and ballast ohms and battery voltage well duhhhhhhhhhhh.
NOTE the coil must be matched (its ohms value) to the current rating of the elec switch or you could burn up the switch CHECK WITH PERTRONIX. Just because its an ELECTRONIC switch versus mechanical contact points doesnt mean you can pump a ton of current through it and you cant use it to switch more current then its rated for anddddddddddddddd its the ohms value of the coil (+ any series ballast) that determines how many amps the switch is handling.
Basically IFFFFFFFF Pertronix says KEEP THE BALLAST that tells me their switch isnt rated to handle all the extra current that would result if you used a 6 volt coil (which could also overheat due to excess current from a 12 volt battery) unballasted !!!!!!!! DO WHAT THEY SAY THEY KNOW THE SWITCH RATING NOT US GUYS HERE. Of course, if you bought a new 12 volt coil (NO ballast required) and its internal primary resistance is near what a 6 volt coil PLUS BALLAST is,,,,,,,, THEN THE CURRENT IS THE SAME AND NO BALLAST WOULD BE NEEDED
Hope this explains the theory and answers your questions NOW CHECK WITH PERTRONIX SO THE COIL PLUS ANY BALLAST DOESNT EXCEED THE SWITCHES RATING
John T
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