641 6 volt coil question

[Tony Jacobs]

No, you have not removed 12 volts. You have dropped the voltage to the primary of the coil by 6 volts. When you have two equal resistances in series, half of the total applied voltage to the circuit is applied to each of the two resistances.

So what you are saying here is that on a tractor that has a 12 volt system that YOU installed a 6 volt ONLY coil that has 1.5 ohms resistance built in to it plus you added a 1.5 ohm external resistor in the circuit to use it with 12 volts so that it doesn’t burn the points you now have only 3 volts left to fire the spark plugs when starting the tractor ? Since the saturation point of a 6 volt coil is only 6 volts that means according to you there is only 3 volts left to fire the plugs . After all the circut from the coil to distributor is now the same as a 6 volt tractor because of the 6 volt ONLY coil that you installed . So when we add in voltage loss from the draw of the starter cranking the engine who knows if there is even 3 volts left to fire the plugs . We won’t bother to get into temperature differences because as we already know that temperature affects voltage also and it also affects atomization of fuel . Fuel atomizes into smaller droplets the warmer the weather and larger droplets as the weather gets colder making the cold weather fuel much harder to ignite especially when lacking the voltage to produce the spark . This extremely low voltage is why a 6 volt tractor with a 6 volt coil seems to start every time just as you release the starter button because that little extra voltage spike from releasing the draw caused by the starter increases the spark just enough to start the tractor . This also explains why Soaked had to make a jumper wire to jump the resistor on the 8N tractor with the 6 volt coil that was converted to 12 volts because that tractor also does not have enough voltage to fire the plugs . He also stated that it ran ok once it was running and the alternator kicked in to raise the voltage back up . That was in his post claiming 6 volt ONLY coils work on 12 volt conversions . This is the same problem ole Fred has with his other tractors , the 961 and the 851 that he spoke about in his post if in fact they have 6 volt ONLY coils on them as he said and the same problem he will have with the 641 that he is using a 6 volt ONLY coil while converting it to 12 volts if you want to call it that .

 

[Sean in PA]

So what you are saying here is that on a tractor that has a 12 volt system that YOU installed a 6 volt ONLY coil that has 1.5 ohms resistance built in to it plus you added a 1.5 ohm external resistor in the circuit to use it with 12 volts so that it doesn’t burn the points you now have only 3 volts left to fire the spark plugs when starting the tractor ?

You apparently don't understand basic electric theory. First, I didn't install anything, Ford installed a coil with a 1.5 ohm primary AND a 1.5 ohm resistance wire on their 1965-1975 tractors. The primary of the coil has 6 volts across it all of the time. I did not say anything about 3 volts. The Ford engineers also installed a bypass wire from the solenoid to the coil primary so that the coil gets the full 12 volts while the starter is turning, but only while the starter is turning so that the points will last.

 

[Tony Jacobs]

You apparently don't understand basic electric theory. First, I didn't install anything, Ford installed a coil with a 1.5 ohm primary AND a 1.5 ohm resistance wire on their 1965-1975 tractors. The primary of the coil has 6 volts across it all of the time. I did not say anything about 3 volts. The Ford engineers also installed a bypass wire from the solenoid to the coil primary so that the coil gets the full 12 volts while the starter is turning, but only while the starter is turning so that the points will last.

You obviously have no idea what you are talking about . We are not talking about 3 cyl 12 volt tractors . The debate you keep avoiding is your constant lie that a 6 volt ONLY coil works on a 12 volt conversion which it does not nor ever will .

 

[Sean in PA]

You obviously have no idea what you are talking about . We are not talking about 3 cyl 12 volt tractors . The debate you keep avoiding is your constant lie that a 6 volt ONLY coil works on a 12 volt conversion which it does not nor ever will .

You are the one that asked for an example of a Ford tractor that came from the factory with a 12 volt system and a 6 volt coil and an external resistor. The 1965-1975 3 cylinder Ford tractors are that example. You keep insisting that a 6 volt coil and one marked "12 volts external resistance required" are not the same thing, while I know that they are the same thing.

This is the result of a Google search for "what is the difference between a 6 volt coil and one marked "12 volts external resistance required":

There is no electrical difference between a standard 6-volt coil and one marked "12 volts external resistance required". They are functionally identical. Both feature a primary resistance of 1.5 ohms. The labeling simply dictates how you wire the system.

 

[Tony Jacobs]

You are the one that asked for an example of a Ford tractor that came from the factory with a 12 volt system and a 6 volt coil and an external resistor. The 1965-1975 3 cylinder Ford tractors are that example. You keep insisting that a 6 volt coil and one marked "12 volts external resistance required" are not the same thing, while I know that they are the same thing.

This is the result of a Google search for "what is the difference between a 6 volt coil and one marked "12 volts external resistance required":

Since your fountain of misinformation is overflowing once again we will correct it . Absolutely no Ford 3 cyl tractors built from 1965 through late 1974 used an ignition bypass wire EVER ! Those particular tractors used Ford part number coils 1) FAC12029A and 2) D2AF12029A these are both external resistor type coils and used the resistance wire in the wiring harness . HOWEVER in late 1974 Ford redesigned their coils the new revision D5TE12029A coil still used the resistance wire in the harness and they added the bypass wire to the system to correct a starter draw problem weakening the spark during cranking . Again Ford NEVER installed a 6 volt coil on a CAR , TRUCK or TRACTOR with a 12 volt system EVER . Again I will say prove your lies with Ford part numbers and Ford literature proving they did that . I have never asked for example of something Ford NEVER built because I know they NEVER built one that way . You can keep insisting what you want but you have not proven anything with Ford part numbers showing that they actually did it which of course they did not . Your Google search means absolutely nothing because it details no FORD information just broad based nothing . This debate started when you claimed you could use the original 8BA12029 Coil which is a 6 volt ONLY coil on his 12 volt conversion if you want to call it that on his 641 . That’s what ole Fred was asking about go back and read his post . Then Soaked chimed in and also said it will work when it will not . You keep changing the subject trying to muddy the waters with your B.S. because you can’t prove anything through Ford .

 

[Sean in PA]

Apparently you do not understand that a coil that requires an external resistor in a 12 volt circuit is a 6 volt coil, regardless of what the manufacturer of the vehicle called it. I understand that you have lots of experience with Ford tractors. Please take a coil from a 12 volt Ford tractor that requires an external resistor and a coil from a 6 volt tractor and measure them with am ohm meter and let me know any differences that you find.

 

[Hobo,NC]

Since your fountain of misinformation is overflowing once again we will correct it . Absolutely no Ford 3 cyl tractors built from 1965 through late 1974 used an ignition bypass wire EVER ! Those particular tractors used Ford part number coils 1) FAC12029A and 2) D2AF12029A these are both external resistor type coils and used the resistance wire in the wiring harness . HOWEVER in late 1974 Ford redesigned their coils the new revision D5TE12029A coil still used the resistance wire in the harness and they added the bypass wire to the system to correct a starter draw problem weakening the spark during cranking . Again Ford NEVER installed a 6 volt coil on a CAR , TRUCK or TRACTOR with a 12 volt system EVER . Again I will say prove your lies with Ford part numbers and Ford literature proving they did that . I have never asked for example of something Ford NEVER built because I know they NEVER built one that way . You can keep insisting what you want but you have not proven anything with Ford part numbers showing that they actually did it which of course they did not . Your Google search means absolutely nothing because it details no FORD information just broad based nothing . This debate started when you claimed you could use the original 8BA12029 Coil which is a 6 volt ONLY coil on his 12 volt conversion if you want to call it that on his 641 . That’s what ole Fred was asking about go back and read his post . Then Soaked chimed in and also said it will work when it will not . You keep changing the subject trying to muddy the waters with your B.S. because you can’t prove anything through Ford .

Decode those part numbers.

 

[Tony Jacobs]

Decode those part numbers.

Doesn’t matter what the part numbers decode to , the FAC number is in the first printing of the 3 cylinder parts book in 1965 and the DA2F is in an updated 1972 edition . I didn’t print the parts books Ford did . I don’t care that some of the numbers decode to car , truck , tractor or industrial engine I just quote the Ford printed parts book , service manual or technical service bulletin .

 

[Tony Jacobs]

Apparently you do not understand that a coil that requires an external resistor in a 12 volt circuit is a 6 volt coil, regardless of what the manufacturer of the vehicle called it. I understand that you have lots of experience with Ford tractors. Please take a coil from a 12 volt Ford tractor that requires an external resistor and a coil from a 6 volt tractor and measure them with am ohm meter and let me know any differences that you find.

Apparently you still don’t understand the difference yet maybe someday you will , probably about the same time you find those elusive 6 volt coil part numbers that work on 12 volt systems that Ford never produced . Oh and by the way according to Ford at serial C438900 in October 1974 is when the bypass wire went into the 3 cyl tractors . So 10 years of production without it good guess you only missed it by 10 years .

 

[Hobo,NC]

8BA-12029
FAC-12029A
D2AF-12029A
D5TE-12029A

Doesn’t matter what the part numbers decode to , the FAC number is in the first printing of the 3 cylinder parts book in 1965 and the DA2F is in an updated 1972 edition . I didn’t print the parts books Ford did . I don’t care that some of the numbers decode to car , truck , tractor or industrial engine I just quote the Ford printed parts book , service manual or technical service bulletin .

So all we know its a coil that fits a ford whatever that ford used across the board on most everything they made up to 1975.

What are the specs on each coil.

 

[Tony Jacobs]

8BA-12029
FAC-12029A
D2AF-12029A
D5TE-12029A

So all we know its a coil that fits a ford whatever that ford used across the board on most everything they made up to 1975.

What are the specs on each coil.

If you have read the entire post from the beginning you would see that the original debate is about one single coil and only one coil the 8BA-12029 6 volt ONLY coil . It was originally manufactured as a 6 volt coil for 6 volt applications beginning with Fords Flathead V8 . It is the only coil listed in Ford Parts Books by Ford from 1948 the beginning of the side mount distributor to the end of 4 cylinder tractor production in 1965 for 6 volt tractors . Ford does list it later as the replacement coil for the tractors in 1967/1969 editions . This debate has nothing to do with the 3 cylinder tractors or anything else for that matter but Sean keeps changing topic that’s all .

 

[Hobo,NC]

If you have read the entire post from the beginning you would see that the original debate is about one single coil and only one coil the 8BA-12029 6 volt ONLY coil . It was originally manufactured as a 6 volt coil for 6 volt applications beginning with Fords Flathead V8 . It is the only coil listed in Ford Parts Books by Ford from 1948 the beginning of the side mount distributor to the end of 4 cylinder tractor production in 1965 for 6 volt tractors . Ford does list it later as the replacement coil for the tractors in 1967/1969 editions . This debate has nothing to do with the 3 cylinder tractors or anything else for that matter but Sean keeps changing topic that’s all .

That's why I asked "What are the specs on each coil" They are all 12029 coils the A is the first revision what changed, calling it a 12V coil is not the answer.

Revision Level: Moving up the alphabet (from A to B, C, etc.) often means the part was updated or revised by engineering.

 

[Keith Williams]

If you have read the entire post from the beginning you would see that the original debate is about one single coil and only one coil the 8BA-12029 6 volt ONLY coil . It was originally manufactured as a 6 volt coil for 6 volt applications beginning with Fords Flathead V8 . It is the only coil listed in Ford Parts Books by Ford from 1948 the beginning of the side mount distributor to the end of 4 cylinder tractor production in 1965 for 6 volt tractors . Ford does list it later as the replacement coil for the tractors in 1967/1969 editions . This debate has nothing to do with the 3 cylinder tractors or anything else for that matter but Sean keeps changing topic that’s all .

Then reply to me Tony if you are sure that a 6 volt coil will not work in a 12 volt system.
I have a 1964 FORD 4000 that had a 6 volt coil when it was converted to 12 volts. A resistor was added to limit the current thru the ignition circuit.
That tractor ran and started just fine. Coil was not changed, starter was not changed, solenoid was not changed.

By the way, it started so easy after the conversion! I could then put real lights on it that I could actually see with at night!

Now when I replaced the coil 2 years ago, all I did was get a coil marked 12 volt use with external resistor. I know that that coil is actually a dirrect replacement for a 6 volt coil. I didn't remove the resistor.

And this whole argument you are having is about you. Sean, Hobo, myself, all realize that a coil doesn't care what the voltage is. They just need the correct amount of current and voltage drop across them to allow them to function. They do that by having the correct resistance.

A coil marked 6 volt has the correct resistance to allow the correct current thru it in a 6 volt system.
A coil marked 12 volt has the correct resistance to allow the correct current thru it in a 12 volt system.

A coil marked 12 volt use with external resistor has the resistance of a 6 volt coil, but can be used in a 12 volt system if the current thru that circuit is limited by an external resister. It also, in a lot of systems, can withstand being fed full system voltage without the resistor while the starter is engaged.

Also, your whole post blaming the GAS for the hard starting in cold weather completely ignored the many other factors that come with cold weather. For example, hydraulic fluid is much thicker, batteries do not produce as much current, etc. BTW, the refineries change the gas formulation when the weather gets colder to make sure it starts just fine.

I hope you all have a GREAT day.

I am headed out to take care of my girlfriend who has pancreatic cancer, there are other priorities in life than arguing about coils!
Keith Williams

 

[Tony Jacobs]

Then reply to me Tony if you are sure that a 6 volt coil will not work in a 12 volt system.
I have a 1964 FORD 4000 that had a 6 volt coil when it was converted to 12 volts. A resistor was added to limit the current thru the ignition circuit.
That tractor ran and started just fine. Coil was not changed, starter was not changed, solenoid was not changed.

By the way, it started so easy after the conversion! I could then put real lights on it that I could actually see with at night!

Now when I replaced the coil 2 years ago, all I did was get a coil marked 12 volt use with external resistor. I know that that coil is actually a dirrect replacement for a 6 volt coil. I didn't remove the resistor.

And this whole argument you are having is about you. Sean, Hobo, myself, all realize that a coil doesn't care what the voltage is. They just need the correct amount of current and voltage drop across them to allow them to function. They do that by having the correct resistance.

A coil marked 6 volt has the correct resistance to allow the correct current thru it in a 6 volt system.
A coil marked 12 volt has the correct resistance to allow the correct current thru it in a 12 volt system.

A coil marked 12 volt use with external resistor has the resistance of a 6 volt coil, but can be used in a 12 volt system if the current thru that circuit is limited by an external resister. It also, in a lot of systems, can withstand being fed full system voltage without the resistor while the starter is engaged.

Also, your whole post blaming the GAS for the hard starting in cold weather completely ignored the many other factors that come with cold weather. For example, hydraulic fluid is much thicker, batteries do not produce as much current, etc. BTW, the refineries change the gas formulation when the weather gets colder to make sure it starts just fine.

I hope you all have a GREAT day.

I am headed out to take care of my girlfriend who has pancreatic cancer, there are other priorities in life than arguing about coils!
Keith Williams

First off you have no idea what coil was on your tractor when you did the conversion to 12 volt . Unless you still have it currently and it is a Ford 8BA12029 coil your experience with this doesn’t matter because you don’t have the coil in question . You and Hobo were not not part of the original debate . It was old Fred , Sean , Soaked(Ed) and myself and it stemmed around Fords original 6 volt only coil manufactured by Ford for 6 volt systems . No modern coils, no aftermarket coils nothing else none of the chinese garbage . You guys all just keep quoting one little sliver of electrical theory . There is no whole post on blaming gas for anything that is just another point that affects real world application of theory and theory on paper . This has nothing to do with the rest of the tractor . I can put the engine on a run stand and make everything equal and eliminate everything to make as equal as possible leaving only the coil , fuel and temperature as the variables .

 

[Tony Jacobs]

That's why I asked "What are the specs on each coil" They are all 12029 coils the A is the first revision what changed, calling it a 12V coil is not the answer.

Revision Level: Moving up the alphabet (from A to B, C, etc.) often means the part was updated or revised by engineering.

According to Ford there is no revisions to the 8BA12029 coil and the part number never changes in any parts book or technical service bulletin that I am aware of . I may not have every single one produced by Ford since I do not have a list of what Ford produced and printed if they even printed such a list . The rest of the coils and or there revisions are not part of this equation .

 

[Sean in PA]

Tony, can you please tell us what the electrical difference is between a 6 volt coil and a coil that is made for a 12 volt circuit that requires an external resistor?

 

[MeanGene1]

Well this has been fun to watch, a bunch of fairly knowledgeable guys being quite aggressively and rudely insulted by another whose ideas on the subject are cast in stone with no chance of being wrong- kinda like watching The View. I haven't been insulted yet this morning, and really don't care, do your worst. When it hit revisions, well I am a 427 Ford guy and am pretty well educated on how and why Ford updated numbers, in particular casting number revisions. Ford did not update numbers unless there was an actual change in the part, which then required a revision- no change, no new number. Now this whole conversion thing, my education came from growing up in my gramps' "home" shop, as he also owned an IH dealership through the years when things updated to 12V systems. He had REO's, Chebbies, IH trucks and tractors, Fergusen etc. The lime spreaders, mostly REO's, had Wisconsin engines to drive the spreaders, special ordered with no charging systems as they ran off the truck system. Then there were the M35 REO/ Studebaker deuce and a halfs that got converted down from 24V to 12V. He was pretty sharp, one of his favorite things was using 6V starters on 12V systems, which despite the naysayers, worked very well. Another was using an 8V battery in a 6V system for better starting- I plowed snow with his old 8N for years, on 8V, and you could dig it out of a fresh snowdrift and it would fire right up- here come the naysayers again. Several years ago, I converted both my side-mount 8N and my 850 to 12V as the original generator systems gave up. I bought the alternator kits from this sight, which claimed that the included alternators would charge from low RPM- which they do. One thing I did, as I have a number of 50's-60's vintage Fords, was convert the tractors to the car-type solenoids with the extra post to bypass the resistance and jump up the coil to 12V, as it is simpler for me and allows me to keep one spare solenoid for all my junk. About now, my personal Voodoo doll is being constructed... As the push-button starter switch on the 8N had crapped out, I converted both tractors to key-start (cue major indignation from the purists). As I spent many years on pony-start CAT stuff where you would be standing on the track while starting, I am thoroughly ingrained to grab the shift lever and confirm neutral. Both of these tractors retain their original 6V coils, using a particular, easy to source MOPAR ballast resistor that works very well. Both tractors start very well, no matter how many reasons one can come up with why they won't/ can't

 

[Sean in PA]

My 1973 17" jet boat with an Oldsmobile 455 V-8 has a 6 volt coil and a Mopar ballast resistor.

 

[MeanGene1]

Yep, I use the Mopar unit as it is inexpensive, very dependable and easy to find, I keep a spare. I am a big fan of stuff that just works

 

[ole fred]

Yep, I use the Mopar unit as it is inexpensive, very dependable and easy to find, I keep a spare. I am a big fan of stuff that just works

How many ohms is it? I'm not trying to start an argument, I want to know. YT says .8 ohms. That doesn't seem like enough.