Does replacement 12 v coil for front dist. needs a resis

marlin54

Member
So I went to Tractor supply and bought a replacement 12volt coil for my *N that had a original 6 volt .and just got tractor and dont now why
but there is a white creamic resistor { the kind you see on older 60's cars on firewall} and mounted close to key . So all I want to know is
if this 12 volt Tractor Supply Coil pack use a resistor or not? There is no where that it says use a external resitor or not needed ...For
Christ sake is it that hard for then to print that information on the box ...?? really ?? you know there is a big difference the leastthey
could do is place piece of paper inside box or print it on box...hate them dog food selling TSC's thats all there good for ...they should
change there name to Dog Food Supply...so do I need to drop the voltage or not ? thanks ahead for answers
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Your first problem is buying any tractor parts from TSC.

That being said..........

Remove the ceramic resistor. All you need on the 12v front coil is the oem ballast resistor.

See tip # 30.
75 Tips
 
Ok Bruce then which is it ? you say no resistor but TIPS75 says on item or notation #30 that allways use a resistor ? I am not sure ?
 


Please re-read tip # 30 and what I said above.

REMOVE the ceramic resistor with a 12v front coil. ONLY use the oem ballast resistor with a 12v front coil.

Do you know what the oem ballast resistor is?
75 Tips
 
marlin54, I had to laugh when I read your post. A TSC opened in my area about a year ago or so. I've been in there maybe 4 times and I feel the same about them as you.
 
I strip out every wire on every tractor I rebuild and convert to 12 volt ...I allways build my own wire set and the only resistor I have on this tractor is that rusty one bolted to back of dash which will not go back on it even if I need to drop the voltage some .So the only question I have is what voltage does the manufacture want for supply voltage to this new replacement ? . they might have built it with a resistance in inside or not ? Either way the item box should come with manufactures requirements for the correct supply voltage so people dont burn it out or damage it , there are no notes on box. .poor manufactures guidance ... but I did just find customer support number on box.. will call monday unless someone knows
 
What is it you need to know that I haven't told you?

Do you really expect TSC to have a clue about that coil?

You need the oem ballast resistor, the only resistor I have on this tractor is that rusty one bolted to back of dash. Broke? Then buy a new one. Or jump it and then buy a new coil.

Your coil should be about 2.25 ohms. You have 14 volts going in it. The oem ballast resistor is .03 ohms cold, 1.7 ohms hot. If you run the coil very long above 4 amps, it will melt.

So do the math.

1.7 ohms + 2.25 ohms = 3.95 ohms. 14 volts/3.95 ohms gets you 3.5 amps. But, no resistor? 8.2 amps. Your coil melts. See why you need that rusty one bolted to back of dash ???
75 Tips
 

Cut and paste this info your search bar after removing the *, it will take you to the TSC page with info about the coil.

https://www.tractor*supply.com/tsc/product/tisco-coil-12v-9n12024-12v
 
so what you are describing to me is a Thermistor . which is basically a resistor that changes its value by temperature , an honestly I dont see the math in that. so your trying to say that the resistance of your 1940's dash resistor changes its value from .o3 to 1.7 ohm and that is possible if it is a thermistor and I doubt my manual here will describe it as such and of course any of these system charging values varies too from 11.5 to 14.5volts so did you not figure that in you electrical theory? ..all this effects the voltage going in ,.and why cant there be just 1 value for a resistor in the middle and between .03 and 1.7 ohms...I dont buy all your math ..I believe a fixed value for a resistor will work . also I dont see why your adding the 2 values together to come up with 3.95 ohms? I dont believe you need that thermistor that you call a resistor that came on the dash . I think it will be fine with just 1 resistor of fixed value that ends up to what the manufactures suggest in supply volts and how about a engine just at idle compared to one at full rpm for long periods..I think that will change the temp of the coil. I think there is a simple solution to this where I can buy just a new resistor and mount it ...
 
I did read that about the 2.5 ohms but does that mean I need to provide a 2.5 ohm resistor or that is the resistance of this coil?
 
Fat finger.

The range is .3 ohms cold to 1.7 ohms hot.

Why do you think Ford used thermistor instead of a fix resistor that you want to used?
75 Tips
 
because like usual with Henry Ford someone else all ready had a better way to do it with out using a thermistor and he did not want to pay for the use of their patent so he came up with this idea where others found a way to do it with just a fixed less complicated way. I dont believe other manufactures used the thermistor ...why?
 
It's because of the design of the coil, circa 1932 on the first Ford V-8.

You need to keep running coil voltage below 4 amps.

You oem ballast resistor is .3 ohms cold, 1.7 ohms hot. The 12v coil is about 2.25 ohms. 14.5 volts running. That gets you 3.67 amps.

For a sure start, you need more than 5 amps; the oem configuration gets you 5.7 amps.

The value of a ceramic resistor is unknown, but it's FIXED and is usually around 2 ohms. Some are more, some less. So, will running current at 3.4 amps is fine, that is also what you get for starting current; it's way too low and will get you a weak spark.
75 Tips
 
You can lead a horse to water but you can't make it drink.

If you're just going to keep arguing until people tell you what you want to hear, why ask the question in the first place?

The variable resistor actually has an even more important role. The current through the ignition system varies with RPM i e a stopped engine with points closed allows much more current than a running engine with points opening and closing. So the resistor gets hot with high current and automatically reduces current to keep from burning the coil up.... once the engine is running the current goes down, the resistor cools down, and allows more voltage than a fixed resistor would.

The same conditions that would heat up the coil, heat up the resistor first, and reduced power to the coil to protect it.

Self regulating, simple, functional.

This post was edited by Smokeonthewater on 08/07/2021 at 06:21 pm.
 
(quoted from post at 15:57:57 08/07/21)
Cut and paste this info your search bar after removing the *, it will take you to the TSC page with info about the coil.

https://www.tractor*supply.com/tsc/product/tisco-coil-12v-9n12024-12v

I went to the TSC link and it states the coil has 2-1/2 Ohms of resistance (which is believable), but further on there's a comment by "DanielB" (from 5 years ago) "This will not require a resistor.".

I'm calling "BS" on that, as others have told you, use the OEM "PTC" resistor.

Don't be so fixated on the "voltage", the MOST important thing is to use a resistor that will limit the primary current to around 4 Amps or a little less with a fully-charged battery and the engine stopped with the points closed.

A couple of minutes will be needed for the "PTC" resistor to heat up and the current to stabilize, don't continue the test for much more than a couple of minutes so as not to damage the breaker points and coil.

(ASSUMING you have an OEM resistor or an aftermarket unit that is actually made to match the original.)
 
Im doing this tractor for my kid as he drug it home in pieces but has alot of new parts ,super good deal .Its a 9n with a 8n motor but has
the front distributor? So unfortunantley I cant change that or I would . stuck with what I got. I will get a new thermistor one just to
finnish this thing up and get it out of my shop . If from the beginning the manual , and if everybody here would have called it what it
really is then I would have understood the logic but I had to drag it out of everyone that it is actually a thermistor not a resistor. and
my manual just calls it a resitor also. . Fords front mounted idea was not a good one no matter how they try to defend it as its in the
wrong place and hard to work on and that is why they finnally went to the side mounted ..This reminds me of Fords Idea of the twin front I
beam they used for so long. .works good for about 20k miles then you cant keep it between the yellow lines but rather than change it to
indeprndent suspension like GM nd admit it was not good they refused for decades untill some finally gave in and changed it to independent
suspension.... looks like the same reasoning was with this front distributor .
 
Ha! I wouldn't buy dog food, a nut, bolt,(same with Fastenal) or any tractor part at TSC. They are an overpriced, overstocked, hardware store with pet food and clothes. Years ago TSC did stock quality tractor parts (TISCO), implements, and parts but no longer since they had new owners take over and don't know diddly squat about anything. You doubt? Ask your TSC clerk that resistor question. See? The most misunderstood features on old FORDs are the 6V/POS GRN electrical system and the Front Mount Distributor. If you force-mount the Front Distributor down, the second you apply power you will bust the aluminum base and render it useless junk. The distributor must be tuned up off the tractor and on your bench. Points (Blue Streak) set and timed correctly, unit tested then mounted correctly. The FORD Front Distributor uses the 12250 Ballast Resistor REGARDLESS if you use the OEM 6V/POS GRN system or do a 12V switch-over job. IF you plan on doing a 12C switch-over job, and plan on using your OEM 6V coil, then you must add an inline 1-OHM (white ceramic style typical) external resistor in the coil circuit. You can omit the extra resistor (my personal preference) simply by replacing the 6V coil with a 12V coil. With a 12V conversion, you remove the GEN and the VR from the circuit and replace with a 12V battery and an ALT. Regardless if 6V (GEN & VR) or 12V (ALT) you must use a fan belt tensioning device attached otherwise you will never charge the battery. ALL wiring must be correct including the proper battery cables.


FORD 8N TRACTOR WIRING DIAGRAMS:
PRIOR TO S/N 8N-263844:
MXLPPwsh.jpg
CfuUUP3h.jpg
rxNF128h.jpg
lz8RwfQh.jpg

FORD N-TRACTOR FRONT MOUNT DISTRIBUTOR:
2P5ECL5h.jpg
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HOW TO SET TIMING:
nM5tfJNh.jpg

RESULTS WHEN UNIT IS MOUNTED 180 OFF:
fqKAmFuh.jpg
UwHSwizh.jpg

FORD 8N-SERIES TRACTOR OEM 6V/POS GRN WIRING PICTOGRAM:
TBC19a5h.jpg

FORD 8N TRACTOR w/FRONT MOUNT -12v CONVERSION:
noSTej6h.jpg

*NOTE: With an OEM 6V coil, you must add an inline 1-OHM external resistor in the circuit labeled the BROWN wire in pictogram. If you opt to swap out the 6V coil with a 12V coil the extra resistor is not used.



*PICTOGRAMS courtesy of JMOR

FORD OEM BALLAST RESISTOR -USED ONLY WITH FRONT MOUNT DISTRIBUTOR:
swlv82hh.jpg
FIK0D4Ih.jpg

HELP: The LH resistor Terminal Post connects to the COIL Stud Terminal Post as you face the back off dash. OEM Wiring is RED.

EXTERNAL 1-OHM CERAMIC RESISTOR - USED ON FRONT MOUNT 12V CONVERSION ONLY IF THE COIL IS 6V:
XRLi3vSh.jpg


FORD TRACTOR FRONT MOUNT DISTRIBUTOR FIRING ORDER; 1,2,4,3 CCW:
Tbt5WvEh.jpg


Breaker Points/Front Mount = .015; Spark Plugs Champion H12 or AUTO-LITE 437 14mm gap at .025-.028; Firing Order: 1, 2, 4, 3 CCW.



FORD 8N TRACTOR ESSENTIAL OWNER/OPERATOR/PARTS/SERVICE MANUALS:
qI9P22kh.jpg



Tim Daley(MI)
 
(quoted from post at 20:49:57 08/07/21) because like usual with Henry Ford someone else all ready had a better way to do it with out using a thermistor and he did not want to pay for the use of their patent so he came up with this idea where others found a way to do it with just a fixed less complicated way. I dont believe other manufactures used the thermistor ...why?
No.
Henry Ford used the ballast resistor because this was the most reliable for starting, while providing a long lasting ignition system.

The cranking of the starter greatly reduces the current available to the ignition system. So early ignition systems were designed to create enough spark to start an engine, while cranking the starter. Once started though, and the cranking load was no longer there, the amount of current was too great for the ignition system, thus the ballast resistor.

Not sure if all manufacturers of early automotive systems used a ballast resistor or not, but systems that did, would start easier than systems with a fixed resistor (or wire), and would last longer than systems that used no resistor at all. Some systems did use a fixed resistor with a bypass while cranking.

Modern systems dont need a resistor as the system can still be designed to start with the lower current while cranking, but can then tolerate higher running current without the draw of a starter cranking.


(quoted from post at 08:50:09 08/08/21) If from the beginning the manual , and if everybody here would have called it what it
really is then I would have understood the logic.......
but I had to drag it out of everyone that it is actually a thermistor not a resistor
Umm...No
It is not a thermistor, it is a ballast resistor. They are not one and and same, similiar yes, the same no.

This post was edited by jimtrs on 08/08/2021 at 08:36 am.
 
Im a little confused . First of all I stripped every wire and electrical part out. I have a 12 v battery, I have a 12 GM 10SI alternator which my electrical guy builds them for me ..it has #2 wire attached to output lub and it does self energizes itself with a little throttle, I have bought a 12 volt coil and just want to know if it needs a std 1 ohm white ceramic resistor or do I need to use the varible resistor from dash.?
 
thanks for comment but if it was so good why did they eventually change it to side mount and get rid if that old style front mount coil ?
 
(quoted from post at 11:53:30 08/08/21) thanks for comment but if it was so good why did they eventually change it to side mount and get rid if that old style front mount coil ?
...varible resistor from dash.?". I don't recognize the term "varible"? But if somehow you wound up with a variable resistor, that is also known as a potentiometer on your dash, then you can just turn the knob until current is correct....just like radio volume control or light dimmer. I have not seen such an installation myself, but I haven't seen everything. Did you drill the dash so that you can adjust it from the operator's position?
 
I used the term varible resistor but meant Thermistor which is a varible resitor but not a manual adjust the original resistor from ford is a
Thermistor that the Ohm value changes by tempurture
 
(quoted from post at 12:18:45 08/08/21) I used the term varible resistor but meant Thermistor which is a varible resitor but not a manual adjust the original resistor from ford is a
Thermistor that the Ohm value changes by tempurture
did a search & I simply can not find a varible anything!
 
Ford had a round coil on the Model A , 1928-1931. And kept it on the Model B 4 cylinder until 1934.

If the Ford side coil of the time was a better option than a front coil, Ford would have used it.
75 Tips
 
(quoted from post at 11:53:30 08/08/21) thanks for comment but if it was so good why did they eventually change it to side mount and get rid if that old style front mount coil ?
Your welcome Marlin.
IMHO I believe Ford was already using a version of the front mounted distributor in vehicles, and carried that into his tractors. As I said in my earlier post
Modern systems dont need a resistor as the system can still be designed to start with the lower current while cranking, but can then tolerate higher running current without the draw of a starter cranking
Back in the day, by 1950, the side mounted distributor with a round can coil was more "modern". Was definitely more robust and the round coil could handle the range of current without a resistor and without overheating

This post was edited by jimtrs on 08/08/2021 at 11:04 am.
 
So now we're up to two pages of posts and still don't understand that yes you need the original resistor block behind the the same as the tractor needed when it was new...

Or a new version of the original but yes you need it.
 
Marlin -

I don't want to disagree with all those who desperately want to perpetuate Henry Ford's 1940 ignition system - and so I shall simply explain what I did with my 1940 9N.

It had been converted to 12 V, Neg ground before I bought it. Over 80 years it had been "maintained" to the point that did not start or run well. I ended up ripping every wire out, along with the various resisters (some abandoned) and, of course, the points and square coil. Pertronix Electronic Ignition kit, new plug cap, new wires, new plugs and a Pertronix round coil modification kit (with internal resister inside the coil) to remove, forever, the 100+- year old make-do engineering.

My 9N now starts instantly in all weather, and runs just as reliably as any modern vehicle.

Now, that's what I did. I was unpopular with some here for NOT wanting to faithfully adhere to Henry's pre WWII electrical engineering ideas. The bottom line is that I now have a superior, modern ignition system that is pretty much plug 'n play with a yearly maintenance check of the spark plugs.

Yeah, without a doubt - "If Henry would-a had the reliable modern ignition systems he would-a used 'em."

So, use what I did or not - it's, of course, up to you. Best of fortune on your project.

- Joe -

This post was edited by Joe.S.AK on 08/08/2021 at 11:29 pm.
 
It would have been helpful for marlin to post up front if he was using the OEM 12250 Ballast Resistor. I think his question is if he needs to add an external 'variable' or 'thermistor' or whatever he wants to call it in the circuit. On the contrary, we have answered the question, however, that with the FORD Front Distributor and square can coil, you must use the OEM Ballast Resistor in the circuit regardless if you are wired for the OEM 6V/POS GRN system or are using a 12V/NEG GRN switchover job. The 1-OHM external resistor comes into play ONLY if you opt to keep your 6V coil when switching over to a 12V system. It connects in line with the coil terminal post wire to the Ballast Resistor post. You omit the extra resistor only if you opt to replace the coil with a 12V coil. That's it, spelled out once again and there are no other alternatives. The ESSENTIAL MANUALS; 75 Tips for N-Owners by Bruce(VA); and WIRNG PICTOGRAMS by JMOR are your best tools and are required reading if'N ya wanna be an N-Owner. I've worked on over a hundred or two N's in my life and have seen just about every wiring fiasco there is. Don't go by how grandpa Joe did it or some shadetree mechanic up the road who works on cars and tractors. Chances they were done wrong, especially if converted to 12V.


Tim Daley(MI)
 

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