641 6 volt coil question

[Hobo,NC]

Read this also ! View attachment 159761View attachment 159755View attachment 159756View attachment 159760View attachment 159758View attachment 159754View attachment 159759View attachment 159757View attachment 159753View attachment 159757

Pix 2 today we call coil ramping its common to check coils this way and the most effective fast way. On modern vehicles its not easy to scope the secondary and normally not worth the time it would take. Then add in one small mistake the possibility of damage to your scope. Today we have misfire counters that are fairly accurate so unless you are a ungodly fast scope guru that only works on one make and model and the coils are EZ to access follow the code/misfire counter. If I have to pull a scope out I am in deep do-do.

4) Spark burn duration (burn time) is what is going on in the cylinder, Lean, rich, low compression burn that into your brain life will be good. I have not read all you posted I still have a day job.

I guess I did not ask the right question. I have another why did it take to so long to post that info?

 

[Tony Jacobs]

Pix 2 today we call coil ramping its common to check coils this way and the most effective fast way. On modern vehicles its not easy to scope the secondary and normally not worth the time it would take. Then add in one small mistake the possibility of damage to your scope. Today we have misfire counters that are fairly accurate so unless you are a ungodly fast scope guru that only works on one make and model and the coils are EZ to access follow the code/misfire counter. If I have to pull a scope out I am in deep do-do.

4) Spark burn duration (burn time) is what is going on in the cylinder, Lean, rich, low compression burn that into your brain life will be good. I have not read all you posted I still have a day job.

I guess I did not ask the right question. I have another why did it take to so long to post that info?

Not to worry my scope is a Sun model 1120 , currently 57 years old and points ignition only . I was giving everyone a chance to prove their point which of course no one did . Plus I was limited on how many pages I could post at once . Standard Electrical engineering was over 30 pages . GM Electrical engineering course for Mechanical Engineers got me down to about 20 pages . So I dumbed down to 1978 Freshman class Voc - Tech high school Auto Shop course using my Sun Scope to eliminate everything except points type ignition and that got me down to 9 pages .

 

[Tony Jacobs]

Please, read post #91 again.
Same coil with same voltage drop, what differs?

Do you know how to read ? The first paragraph on the first page clearly explains it . It is TWO different coils both with 1.5ohms resistance so both coils require a 1.5ohm resistor to be used on a 12 volt system . This is all based on a 1978 high school Auto Shop basic ignition course using a 57 year old Sun model 1120 Scope . I can’t dumb it down any further because I never saw a basic ignition course taught in pre-school , kindergarten or first grade . So if you can’t comprehend 9th grade I don’t know what to tell you .

 

[Tony Jacobs]

Oh my goodness! you just posted the exact thing that you said wouldn't work!
That states that a 6 volt coil at 1.5 Ohms works with an external resister of 1.5 Ohms in a 12 volt system just fine.
It also states that the newer designed coil works better. Something that no one here has a problem with. At least I don't, because that's what I replaced my 6 volt coil with when it finally died.

BTW Tony, concerning my 1964 Ford 4000. I found the boxes from the last 3 coils I got. The 6 Volt coil was on it and died. More than likely in the late 1990's. I remember raking hay and it just died. Was it the original coil, no idea, I just know it was the coil on it when I had it converted from 6 to 12 volts in 1986. Local AG teacher at Tech school did it when tractor was in for a rebuild. Cam shaft gear blew up. He added a Ballast Resistor to the wiring, put a Delco 10SI on it. I could finally put some lights on the 4000!

I went to the local Ford dealer, they sold me this:
CNH Original parts E8TF12029BA Made in Mexico - Didn't last long, going thru field with a rear scoop full of dirt and it just died. Lasted maybe 5 Years.
Lets say early 2000's. It was replaced by:

TISCO 290317 replaces Ford D5TE12029AB Made in USA
OEM applications
FORD TRACTORS
2000-3000-4000-5000 1965/UP
2600-3600-4600-5600-6600 1975/UP
12-VOLT
GEEEEEEE that says all the X000's from 65 up!

That coil still works, but I was chasing a short in the system and did an upgrade to all Blue Streak products.
Current coil:

Standard Blue Streak FD471
Made in Mexico.

Tony, you can have all those fancy tech documents and diagnostic tools, but when I am out in a field with hay down, I just need the tractor to RUN.
I think that was all any of us wanted, a Tractor that runs. We are not working on hot rods.

BTW, I can see that the wiring on the 1974 2000 I have is original. You can tell because the cloth over old wire with original ends on the wire.
I got it in 2023 after my cousin died. He was the second owner.

Have a GREAT day!

I suggest you read the FIRST paragraph on the FIRST page again because it states nothing that you are saying . So since you have no idea what coil was on it when your 64 4000 was converted , using that as an example is a moot point at best . According to Ford’s Consumer Electrical Technical bulletin number T-5 dated 12/89 coil E8TF-12029-BA is a Universal 6volt / 12volt coil . I have no idea what the construction of it is so I am not surprised they don’t last long . If you take into account the problems of using a 6 volt coil on a 12 volt system and using a 12 volt coil on a 6 volt system it’s a wonder they even bothered to build a coil like that . Ford coil D5TE-12029-AB is a 12 volt external resistance coil listed in a 1975 3 cylinder tractor parts books when the wiring harness had a resistance wire in it . Those Fancy Tech Documents you are referring to are a 1978 Voc-Tech High School Auto Shop course I took as a kid . The Fancy Diagnostic Tools you are referring to is my 57 year old Sum Model 1120 Scope for Points Ignitions ONLY . They were built from 1969-1977 just the type Dealerships bought back when these tractors were new . So if you can’t read and comprehend at a High School Level I can see why you arguing about this . As I said before Ford stated the date and serial number for the Wiring Harness change in a Service Bulletin which was October 1974 . Then a 1979 Ford Tractor parts book revision lists the change as August 1974 and yet again a 1990’s reprint of the same 1965-1975 Ford Tractor parts book list the change as October 1973 so regardless of which one is actually correct it did not happen in 1965 as Sean said it did . Since Basic Ignition courses were not taught in Pre-School , Kindergarten or First Grade I can’t dumb it down below 9th grade .

 

[Hacke]

Do you know how to read ? The first paragraph on the first page clearly explains it . It is TWO different coils both with 1.5ohms resistance so both coils require a 1.5ohm resistor to be used on a 12 volt system . This is all based on a 1978 high school Auto Shop basic ignition course using a 57 year old Sun model 1120 Scope . I can’t dumb it down any further because I never saw a basic ignition course taught in pre-school , kindergarten or first grade . So if you can’t comprehend 9th grade I don’t know what to tell you .

English is not my native language, but I can read and understand what I wrote in post #100:
"
Please, read post #91 again.
Same coil with same voltage drop, what differs?
"

Post #91 is this post:

H

Post in thread '641 6 volt coil question'

Tuesday at 5:14 AM

Tony,

Let us say that you have a 6 V system with a 6 V ignition coil, that have a primary winding resistance of 1.5 Ω.
You convert to a 12 V system, keep the ignition coil and add a 1.5 Ω resistor in series with the primary winding.
That is the only thing you change in the ignition system.
Same amount of current (4 A) goes through the primary winding in both cases.
There is a 6 V drop across the primary winding in both cases.

What differs in the ignition coil's function/performance?

.

• Hacke

• 

 

[Tony Jacobs]

English is not my native language, but I can read and understand what I wrote in post #100:
"
Please, read post #91 again.
Same coil with same voltage drop, what differs?
"

Post #91 is this post:

H

Post in thread '641 6 volt coil question'

Tuesday at 5:14 AM

Tony,

Let us say that you have a 6 V system with a 6 V ignition coil, that have a primary winding resistance of 1.5 Ω.
You convert to a 12 V system, keep the ignition coil and add a 1.5 Ω resistor in series with the primary winding.
That is the only thing you change in the ignition system.
Same amount of current (4 A) goes through the primary winding in both cases.
There is a 6 V drop across the primary winding in both cases.

What differs in the ignition coil's function/performance?

.

• Hacke

• 

You are using the same coil that DOES NOT work in both 6 volt system and a 12 volt . A 6 volt coil works in the 6 volt system just fine it DOES NOT produce enough spark in a 12 volt system . So you ARE NOT reading and comprehending what I wrote . My test is very simple it compares a 6 volt coil with 1.5 ohms resistance to a 12 volt coil with 1.5 ohms resistance ( which is a externally resisted coil ) both coils require a 1.5 ohm resistor in the 12 volt system , THAT IS TWO DIFFERENT COILS . HOWEVER if you read what I posted the 12 volt coil with the 1.5 ohm resistance in it requiring a 1.5 ohm resistor to used in its 12 volt system has TWICE AS MANY WINDINGS in it as the 6 volt coil ALLOWING the 12 volt coil to make at least 10,000 volts more on the secondary side than the 6 volt coil . The 6 volt coil has a smaller metal core in it and larger diameter windings but fewer of them . The 12 volt coil has a LARGER metal core . The 12 volt coil has SMALLER DIAMETER but TWICE as many windings as the 6 volt coil . 6 volt coils and 12 volt coil are built as TWO COMPLETELY DIFFERENT coil . You just like everybody else is hung up on primary resistance which means NOTHING because when both coils are same resistance the 12 volt still make more spark and always will . The 6 volt coil will make an ORANGE spark the 12 volt coil will make a BRIGHT BLUE spark because it makes more voltage . You are wrong you will always be wrong because a 6 volt coil will never work on a 12 volt system . Until you realize a 6 volt coil and a 12 volt coil are MANUFACTURED COMPLETELY DIFFERENT INTERNALLY you will always be wrong . The diagrams you keep posting have nothing to do with coil operation or spark production on the secondary side which is what makes it run . Your diagram just shows it won’t burn the points that’s all you and everybody keep talking about . The 12 volt coil will always produce more spark than the 6 volt regardless of what you think or say .

 

[Sean in PA]

Tony, I understand what you are saying about the differences in the two coils, but many people have converted 6 volt systems, including the pre-1965 Ford tractors to 12 volts and never changed the coil and merely added a ballast resistor and they start and run fine for many years. So your statement that it will not work is false.

 

[Keith Williams]

Tony, I understand what you are saying about the differences in the two coils, but many people have converted 6 volt systems, including the pre-1965 Ford tractors to 12 volts and never changed the coil and merely added a ballast resistor and they start and run fine for many years. So your statement that it will not work is false.

Exactly what I did Sean! I took a tractor that was using a 6 volt battery so there for, a 6 volt coil (who cares if it was the original coil it was a 6 volt coil).
I added a ballast resister to the ignition circuit and switched it to 12 volts. As Hacke has shown, Sean and myself have shown and others. Any tractor this is done on, runs just like it did before the switch. The resister limits the current thru the ignition circuit to the same level as it was before the switch. The current flow through the circuit is the key.

I even did the extra research to google "will a 6 volt coil work in a 12 volt system". Car guys also have the same experience. They have a 6 volt system in a car or truck. Switch to 12 volts. Add a ballast resistor to ignition circuit to limit current flow. Their motor runs!

Tony, you are the only person that says it will not work.

The only one.

You try to belittle us by saying we can't read. I will not respond to that to you.

You try to impress us with your schooling. I think you would find yourself lacking if you tried to match some of the others here in their education.

I come here to learn and to help others. In this thread I did learn. Jim enlightened me that there was a solenoid that would work for me on my 1964 4000 keeping the safety features in place and adding the bypass. Thank you, Jim!

Tony, you have a lot of knowledge to share. I was happy to see your recent return to help others. Please continue to help. Just realize that there are others here that also have knowledge to share.

Keith Williams
BS - Physics, Astronomy, Mathematics & Computer Science.
5 1/2 Years working at The Timken Company in Bearing Design and Advanced Bearing design.
16 1/2 Years working at Weirton Steel in various roles including system administration, network design, CAD/CAM systems, system integration, project administration and liaison between the operations departments and the computer department.
2+ Years working at AK Steel as a Senior Process Control Engineer.
2+ Years working at Eli Lilly as a Systems Administrator over their Laboratory Information Systems.
All that while working on my family farm, 240 acres in Eastern Ohio.
Now happily retired!
Have a GREAT day all.

 

[Tony Jacobs]

Tony, I understand what you are saying about the differences in the two coils, but many people have converted 6 volt systems, including the pre-1965 Ford tractors to 12 volts and never changed the coil and merely added a ballast resistor and they start and run fine for many years. So your statement that it will not work is false.

You keep telling yourself that yet you have not provided one shred of proof . No you don’t understand one single thing about the differences in the coils , primary resistance has nothing to do with secondary voltage . All you talk about is primary resistance and adding a ballast which dictates absolutely nothing about whether the coil is 6 volt or 12 volt . You claim to use 6 volt coils yet you have no idea how to tell them apart . As I have said over and over prove it and you don’t .

 

[Tony Jacobs]

Exactly what I did Sean! I took a tractor that was using a 6 volt battery so there for, a 6 volt coil (who cares if it was the original coil it was a 6 volt coil).
I added a ballast resister to the ignition circuit and switched it to 12 volts. As Hacke has shown, Sean and myself have shown and others. Any tractor this is done on, runs just like it did before the switch. The resister limits the current thru the ignition circuit to the same level as it was before the switch. The current flow through the circuit is the key.

I even did the extra research to google "will a 6 volt coil work in a 12 volt system". Car guys also have the same experience. They have a 6 volt system in a car or truck. Switch to 12 volts. Add a ballast resistor to ignition circuit to limit current flow. Their motor runs!

Tony, you are the only person that says it will not work.

The only one.

You try to belittle us by saying we can't read. I will not respond to that to you.

You try to impress us with your schooling. I think you would find yourself lacking if you tried to match some of the others here in their education.

I come here to learn and to help others. In this thread I did learn. Jim enlightened me that there was a solenoid that would work for me on my 1964 4000 keeping the safety features in place and adding the bypass. Thank you, Jim!

Tony, you have a lot of knowledge to share. I was happy to see your recent return to help others. Please continue to help. Just realize that there are others here that also have knowledge to share.

Keith Williams
BS - Physics, Astronomy, Mathematics & Computer Science.
5 1/2 Years working at The Timken Company in Bearing Design and Advanced Bearing design.
16 1/2 Years working at Weirton Steel in various roles including system administration, network design, CAD/CAM systems, system integration, project administration and liaison between the operations departments and the computer department.
2+ Years working at AK Steel as a Senior Process Control Engineer.
2+ Years working at Eli Lilly as a Systems Administrator over their Laboratory Information Systems.
All that while working on my family farm, 240 acres in Eastern Ohio.
Now happily retired!
Have a GREAT day all.

You say the same thing yet you have no proof that you even had a 6 volt coil on it to begin with . You also have no idea how to prove a 6 volt coil from a 12 volt coil because you do not understand the differences between the two and never will . All you have ever shown is your smart enough not to
Burn the points other than that it is completely pointless . Research you did is a joke it doesn’t prove anything because there is no facts to back anything up . If you even bothered to just look in the archives here you find a retired electrical engineer by the name of John T who has been saying the very same thing as I have been years longer than me . Not to mention many others . So don’t worry I am not the only one saying it does not work . I have not said one thing about my schooling nor do I plan to . You have no idea where I have been or what I have done nor do I care if you do . I used my high school auto shop course to make this as simple as possible and my 60 year old Points Only Sun Scope as an example to get the simplest answers yet all you do is talk about primary resistance over and over which neither dictates 6 or 12 volt or secondary voltage to make actual spark at the plugs . So you show me one shred of actual proof that it works and yet you won’t because you can’t .

 

[Tony Jacobs]

You say the same thing yet you have no proof that you even had a 6 volt coil on it to begin with . You also have no idea how to prove a 6 volt coil from a 12 volt coil because you do not understand the differences between the two and never will . All you have ever shown is your smart enough not to
Burn the points other than that it is completely pointless . Research you did is a joke it doesn’t prove anything because there is no facts to back anything up . If you even bothered to just look in the archives here you find a retired electrical engineer by the name of John T who has been saying the very same thing as I have been years longer than me . Not to mention many others . So don’t worry I am not the only one saying it does not work . I have not said one thing about my schooling nor do I plan to . You have no idea where I have been or what I have done nor do I care if you do . I used my high school auto shop course to make this as simple as possible and my 60 year old Points Only Sun Scope as an example to get the simplest answers yet all you do is talk about primary resistance over and over which neither dictates 6 or 12 volt or secondary voltage to make actual spark at the plugs . So you show me one shred of actual proof that it works and yet you won’t because you can’t .

So in closing if you guys and your technical brilliance is so great and you continue to say the 6 volt parts work fine on 12 volt systems , especially coils then why did Ford in 1956 when Automotive and Truck lines were converted 12 volt , Ford redesigned every Electrical component to used in the 12 volt system as a 12 volt volt component ? Why wouldn’t have Ford just continued to use 6 volt parts and save themselves millions and millions of dollars in design , engineering and manufacturing costs ? Why in 1958 when Ford brought out their Diesel Tractors ( 501/601/701/801/901) with 12 volt systems did they again redesign all of the Electrical Components for use with the new 12 volt system ? Why didn’t just keep using all the 6 volt parts and save themselves millions and millions of dollars again in redesign , engineering and manufacturing costs ? After all if you guys technical brilliance is so great Ford had two years to prove that the 6 volt parts worked just fine and there would have been no need to make more 12 volt parts since they were not needed . But you see in the real world 6 volt parts don’t work on 12 volt systems , especially coils so Ford did in fact have to design , engineer and manufacture both 6 volt and 12 volt parts to make both systems work and operate properly . Since Ford as way more Design , Engineering and manufacturing experience than you guys and all of your technical brilliance I will continue to stand by exactly what I said and especially since no one has any shred of proof that it actually works other than just hearsay . So this matter is closed as far as I am concerned .

 

[Hacke]

You say the same thing yet you have no proof that you even had a 6 volt coil on it to begin with . You also have no idea how to prove a 6 volt coil from a 12 volt coil because you do not understand the differences between the two and never will . All you have ever shown is your smart enough not to
Burn the points other than that it is completely pointless . Research you did is a joke it doesn’t prove anything because there is no facts to back anything up . If you even bothered to just look in the archives here you find a retired electrical engineer by the name of John T who has been saying the very same thing as I have been years longer than me . Not to mention many others . So don’t worry I am not the only one saying it does not work . I have not said one thing about my schooling nor do I plan to . You have no idea where I have been or what I have done nor do I care if you do . I used my high school auto shop course to make this as simple as possible and my 60 year old Points Only Sun Scope as an example to get the simplest answers yet all you do is talk about primary resistance over and over which neither dictates 6 or 12 volt or secondary voltage to make actual spark at the plugs . So you show me one shred of actual proof that it works and yet you won’t because you can’t .

I took a 'look in the archives' and found this, posted by member John T:

"...
One way to look at it is if you have a 12 volt tractor but a 6 volt coil plus an external ballast (may or may NOT be your case), the ballast would be the same resistance of the coil to form a 50 50 voltage divider thus dropping 6 volts across the ballast and 6 across the coil.
..."

J

Post in thread 'What is the ohm value of this resistor?'

Jul 23, 2025

Good info from wore out. One way to look at it is if you have a 12 volt tractor but a 6 volt coil plus an external ballast (may or may NOT be your case), the ballast would be the same resistance of the coil to form a 50 50 voltage divider thus dropping 6 volts across the ballast and 6 across the coil. Some cheaper VOMs are NOT real accurate in the low ohms range so get your volt meter and measuer the voltage drops across the coil and ballast and see what ohms it shows ??? My best pure and worthless guess is the resistor is in the 1.5 ohms range.

John T

• John T

• 

 

[Keith Williams]

I took a 'look in the archives' and found this, posted by member John T:

"...
One way to look at it is if you have a 12 volt tractor but a 6 volt coil plus an external ballast (may or may NOT be your case), the ballast would be the same resistance of the coil to form a 50 50 voltage divider thus dropping 6 volts across the ballast and 6 across the coil.
..."

J

Post in thread 'What is the ohm value of this resistor?'

Jul 23, 2025

Good info from wore out. One way to look at it is if you have a 12 volt tractor but a 6 volt coil plus an external ballast (may or may NOT be your case), the ballast would be the same resistance of the coil to form a 50 50 voltage divider thus dropping 6 volts across the ballast and 6 across the coil. Some cheaper VOMs are NOT real accurate in the low ohms range so get your volt meter and measuer the voltage drops across the coil and ballast and see what ohms it shows ??? My best pure and worthless guess is the resistor is in the 1.5 ohms range.

John T

• John T

• 

Exactly Hacke.
Simple electrical theory.
I put this thread to rest long ago.
Now it's just entertainment!
Keith

 

[Hacke]

Exactly Hacke.
Simple electrical theory.
I put this thread to rest long ago.
Now it's just entertainment!
Keith

Yes, there is nothing more to say on this matter.

 

[Sean in PA]

You keep telling yourself that yet you have not provided one shred of proof . No you don’t understand one single thing about the differences in the coils , primary resistance has nothing to do with secondary voltage . All you talk about is primary resistance and adding a ballast which dictates absolutely nothing about whether the coil is 6 volt or 12 volt . You claim to use 6 volt coils yet you have no idea how to tell them apart . As I have said over and over prove it and you don’t .

So you're saying that if you convert a 6 volt system to 12 volts and do not replace the coil and merely add a ballast resistor, and the tractor runs and starts fine, that somehow the original coil in that 6 volt tractor was a 12 volt coil?

 

[Keith Williams]

So you're saying that if you convert a 6 volt system to 12 volts and do not replace the coil and merely add a ballast resistor, and the tractor runs and starts fine, that somehow the original coil in that 6 volt tractor was a 12 volt coil?

Furthermore, we have to prove it to him.
LOL
Like I said entertainment value!

 

[soaked]

I didn't buy the complete kit as I have plenty of alternators lying around. I did buy two of the resistors and one coil with a resistor. As close as I can tell they measure about .8 ohm. Definitely less than one.

Just curious, do the .8 ohm resistors increase with heat to 1.75 like this one?

 

[ole fred]

I can't say, but I can say is that the one I got looks exactly like the one in your picture.

YT Label reads: Coil Resistor, New, Ford, 8NE103
It also says it is made in India.
Oh yeah, YT also says ASAP#105710 & PC#:RB1001
Mfg Dt : December 25

 

[soaked]

I hoped you might recognize a listing from here at YT.
My aim posting to ole fred was to inform that kit resistors may not be very helpful, if using a 6 volt coil.
But as he bought two .8 resistors, figured he would line em up for .8 + .8 = 1.6 ohms, and thats not too far from 3.0 ohms, if his 8ba12029 has original specs.
I still dont understand what a .6 ohm resistor is doing in a 12 volt conversion kit...
View attachment 159110
Respectfully
John

I can't say, but I can say is that the one I got looks exactly like the one in your picture.

YT Label reads: Coil Resistor, New, Ford, 8NE103
It also says it is made in India.
Oh yeah, YT also says ASAP#105710 & PC#:RB1001
Mfg Dt : December 25

Your resistor #105710 is the .6 ohm pictured in post #37. Guessing it does increase resistance with heat, but just isn't in the listing.
Glad its working!

 

[Sean in PA]

That's an interesting feature, starting out at a low resistance and increasing as it warms up allows for a higher voltage at the coil while starting, so you don't need a bypass wire.