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Subject: 9N coil

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Les Leach    Posted 04-26-2018 at 15:14:31 [URL] [DELETE]        [Reply] [Email]  
  • 9N coil
  • I have been checking the ignition electrical on a 9N that has an alternator conversion to 12 volts. The primary ignition circuit steps down to six volts for the coil, through a resistor. Should I purchase a 12 volt coil and eliminate the resistor? Is there a link to a wring diagram?
    Thanks for the information.

    Les Leach    Posted 04-28-2018 at 12:17:58 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N coil
  • Thank you for the information. I am not including a photo because I can not get Photobucket to respond. The resistor is solid porcelain with tabs on each end. This was in place when it was purchased. On the right side of the resistor is the switched/power (12V) side. The left side is 6V and goes to the coil. From your comments, there should be another resistor in the circuit. I have looked at the pictograms and do not see anything similar to what is on our tractor. All help is appreciated. Also, what is the downside of not having a "stock" resistor in place. At some point I would like eliminate the existing step down resistor and go to a 12V coil.
    I will try to load a photo later today. Between dodging ads on Photobucket and it not responding, to me the site is frustrating to use.

    Tim Daley(MI)    Posted 04-30-2018 at 06:51:51 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N coil
  • The ceramic external resistor to be used on 12-volr conversions using a 6-volt coli only sounds correct -see photo below. WE CAN"T STRESS THIS ENOUGH, but you MUST use the original ballast resistor in any set up using either a 6-volt coil or a 12-volt coil. Failure to have this in the circuit will cause circuit failure and damaged parts. Resistors are non-polarized so it doesn't matter which side is connected to whatever. They are however at a fixed value measured in OHMS (Resistance). Bruce and a few others did some testing a while ago on several ceramic resistors new, out of the box and got values readings all over the place. Don't assume that just because the package states "Rated at 1.2 OHMS" that it is. se your VOLT/OHM Meter and check for yourself.
    Since it appears you have been trying to power this without the original Ballast Resistor in the circuit, like Bruce said, you probably have now fried the coil. You can test the coil with your VM METER but not a true test if good or bad -see BRUCE(VA)'s 75 Tips for more on that. You say 'at some point I want to eliminate the step-down(external) resistor and go to a 12V coil', well this may be that time. Since you now need to buy a new OEM Ballast Resistor and wire it in correctly, and if your 6-volt coil is fried, replace with a 12V coil, you can kill 2-birds, 1 stone. Your call, but you now have been given all the pertinent information needed so have at it and report back.


    Tim Daley(MI)

    Bruce (VA)    Posted 04-29-2018 at 07:15:39 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N coil
  • " At some point I would like eliminate the existing step down resistor and go to a 12V coil. "

    As all of us are telling you.........even with a "12 volt ", you still need the oem ballast resistor.

    " Also, what is the downside of not having a "stock" resistor in place."

    You will melt the coil.

    It's in the math, I=E/R.

    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 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 the ceramic resistor is unknown, but it's FIXED and is usually around 2 ohms. 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.

    Does that explain why you need the oem ballast resistor?

    Les Leach    Posted 04-29-2018 at 20:31:14 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N coil
  • Yes. Thank you

    Tim Daley(MI)    Posted 04-28-2018 at 15:48:25 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N coil
  • LES-
    It doesn't sound like you have the original ballast resistor in your circuit. I think you are trying to tell us your coil is 6-volts. If so, you need to use the additional resistor from coil to ballast resistor post as shown in 4th pictogram. The downside to not using the stock OEM Ballast Resistor is just what you are experiencing -nothing. Since you already have a coil and the 'step down' resistor, adding and wiring correctly a ballast resistor would be the cheapest way to go. Going to a 12-volt coil would eliminate the extra 'step down' resistor that we think you have now -see links below. Either way, when using a 6-volt coil or a 12-volt coil, you WILL need the OEM ballast resistor in place. Getting the right components and wiring them correctly are the key elements here. Bear in mind just because the parts were on the tractor when you bought it doesn't mean they are right to begin with. As stated before, go by the wiring schematics in the Operator's and F-04 manuals for original wiring, then add in alternator and extra resistor as needed.



    Tim Daley(MI)

    Tim Daley(MI)    Posted 04-28-2018 at 14:10:19 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N coil
  • First, you can't post picture for free anymore from PhotoBucket unless you "upgrade" your account and pay $500 per year. Some of us use www.imgur.com now as it is still free.

    Next, this is what was said about the resistor:

    "...you need the original ballast resistor with both the 6 volt and 12 volt coils. What you do not need with a 12 volt coil is an extra resistor in the wire going to the coil. Look at JMOR's pictograms to see that the original ballast resistor is used in both/all setups..."

    Scroll down to the 4th diagram -9N/2N 2-volt conversion and observe the diagram closely. So, first is to answer us this. Is there an OEM Ballast resistor in place? We've posted pictures and the pictograms have sketches of what it looks like.

    Tim Daley(MI)

    Tim Daley(MI)    Posted 04-27-2018 at 04:02:42 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N coil
  • The original ballast resistor looks like this, and can be purchased new at Just8Ns.com - see LINK below. Picture shows Steve Dabrowski's early 8N in restoration mode from a few years ago. On the RH side, viewed from behind the dash, you can see the OEM ballast resistor mounted. If you don't already have the essential manuals for your 9N, many of us N-Owners here suggest you invest in them as well. They are as much a vital tool as any wrench is. The 4/5 manuals on the LH side are the important ones: I&T F-04 Manuals; 9N Owner Manuals; 2N Owner manuals; and the '39-'53 MPC (Master Parts Catalog). Although you now have a 12-volt changeover, it is important to know what the original 6-volt system is like. Having the correct wiring is very important in either situation.



    Tim Daley(MI)

    Bruce (VA)    Posted 04-26-2018 at 17:40:15 [URL] [DELETE]        [Reply] [Email]  
  • Re: 9N coil
  • " a " resistor?

    What does it look like?

    6v or 12v coil doesn't matter, you must use the oem ballast resistor.

    But....if you have a 12v coil, do not use any other resistor.

    And.....if you have a 6v coil and want to keep it, yes, you need another resistor in the circuit. Do NOT just buy one and install it w/o measuring it first, no matter what it is advertised as. A 2 ohm resistor, plus the 1.7 ohms (hot) of the oem resistor will get you below 4 amps running current. 2.5 ohms would be fine too.

    Tim Daley(MI)    Posted 04-26-2018 at 16:03:53 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N coil
  • HiYa Les-
    Yes, there certainly are wiring diagrams and many other useful articles in our HOW-TO's forum. At the top of the NTC Home Page you will see a red menu bar with many other links to other forums. here is a quick link -see below -to get you there fast. You can save the document to your computer and print it out and take right to the barn/shop so it's handy when working on your 9N. Scroll down til you find your setup and go from there. If you have a 6-volt coil, you will need the original ballast resistor. If you have a 12-volt coil, you do not use the resistor. Many 12-volt jobs are done improperly but with JMOR's Wiring pictograms, he has put together every CORRECT way to wire these old N's. Do not deviate from what he has provided as it will most likely cause failure. Note also when doing a 12-volt changeover, that besides the generator being eliminated, the voltage regulator or round can cutout is taken out of the circuit as well. A 12-volt battery and an alternator means using a negative ground system. The original N's used a 6-volt/positive ground system. Feel free to red though the forums, download articles and manuals, and post as many questions you like.

    Tim Daley(MI)

    R Geiger    Posted 04-26-2018 at 16:11:43 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N coil
  • you need the original ballast resistor with both the 6 volt and 12 volt coils. What you do not need with a 12 volt coil is an extra resistor in the wire going to the coil. Look at JMOR's picograms to see that the original ballast resistor is used in both setups.

    Tim Daley(MI)    Posted 04-27-2018 at 05:25:57 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 9N coil
  • Yep, typing before I had coffee...thanks for the correction.

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