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Subject: Ford 2N Ignition Coil Circuit

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Phillip G.    Posted 08-09-2022 at 03:01:03 [URL] [DELETE]        [Reply] [Email]  
  • Ford 2N Ignition Coil Circuit
  • Hey fellows! I cannot find the ignition system diagram that shows what resistance should be at the front mount coil on a 2N. There's a manual that shows the resistors and coil specs somewhere.

    Tim Daley(MI)    Posted 08-09-2022 at 11:16:40 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • You sound like a man who has many questions about his electrical wiring system but were afraid to ask. First of all, there are no OEM FORD MPC’s OPERATOR manuals that outline specifically what each voltage and current readings are on every part and component. OHMS’s LAW is the natural rule of thumb. The I&T FO-4 Manual has a section, ELECTRICAL AND IGNITION SYSTEM, on testing the 9N-10505 Cutout, 8N-10505 Voltage Regulator, and motor testing the starter motor and generator. Do you mean that picture of a front mount 6V coil that JMOR or BRUCE (VA) posted years ago showing what the resistance of the coil to test static? Set your VOM, digital or analog, it does not matter for this test, to OHMS, with Probe #1 on Pigtail of Coil and Probe #2 on the top terminal wire post. Reading should be 1.5 OHMS +/- .3 OHM. Polarity is not important for this test. A 12V coil should read about double the current. It does not mean the coil is good necessarily. That would take an extremely sophisticated and very expensive test unit so don’t read too much into the static test. You must understand the 6V/POS GRN Electrical Wiring System thoroughly and before you attempt to do a 12V switcheroo job. Know what the OEM Ballast Resistor, Cutout Circuit, GEN, Voltage Regulator, AMMETER, Starter Motor, Neutral Safety Start Pushbutton Switch, and Ignition Key Switch are and how each functions, in the systems. Know what a GEN ‘A’ Circuit and a ‘B’ Circuit are and how each are different. All 9N and 2N’s were wired the same after s/n 12500 with a 1-wire/3-Brush Generator and the Round Can Cutout, and a one wire starter motor with NO Solenoid. All 8N’s used a 3-Wire GEN with a Voltage Regulator using the ‘A’ Circuit Design. All this plus knowing how to rebuild, time, test, and mount the front mount distributor correctly; there’s a right way and a wrong way. FACT: 99.98% of all non-starting issues are due to incorrect wiring. Invest in the ESSENTIAL MANUALS and additional documents, WIRING PICTOGRAMS by JMOR, and 75 Tips For N-Owners by Bruce (VA).



    I&T FO-4 MANUAL – 9N-10505-B CUTOUT TEST:


    FORD 9N-10505-B CUTOUT –USED AFTER S/N 12,500 TO S/N 258504 ON 9N & 2N MODELS ONLY:





    Tim Daley(MI)

    Phillip G.    Posted 08-09-2022 at 13:11:04 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • No sir, I wasn't afraid at all. Years ago I had a manual that showed what Ford wanted at the front mount coil concerning specs if a 12 conversion was done. Ohms, amps, voltage, etc.(if memory serves) to prevent smoking the coil. I can't remember years ago but, it seems like I used an inline porcelain resistor with a 6V coil. Anyway, your reply & diagrams really help, and I appreciate that.

    Tim Daley(MI)    Posted 08-10-2022 at 04:29:36 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • I was sort of being flippant about asking questions, but that is why we are here Phil. Gotta be thick skinned if'N ya wanna be an N-Owner!!! Anyway, I usually always first ask too if you are using 6V or 12V like JMOR did. Either system is fine, will run and work just fine, as long as the system is wired correctly for that setup. Each setup has its own PROS & CONS. Many get into trouble when their 6V system becomes non-starting/non-running and they 'think' the only solution is to switch over to 12V. If the system won't run on 6V, why do you think it will on 12V? SEE JMOR's Wiring Pictograms for every correct way to wire them. FORD did not ever use 12V until the late 1950's when the Hundred Series diesel models were introduced. There are no OEM N-Series manuals that show a 12V setup. Many fellas start tinkering with their electrical systems when problems arise and 'think' they know what to check, and what the data should read. This is where they get into trouble as they start probing their VOM for current and voltages and have no idea where to check, why, and what they should be. Worse is the guy who starts probing with his Idiot Test Light and shorts out something. Always use your VOM set to CONTINUITY when testing wiring. A test light requires power and you do not want power to the circuit while tracing wiring. I advise to first disconnect the battery, take it to a shop to be tested. Many times it is the simple basic things that bite us. First thing is to test the battery. The battery is the heart of every machine. You need a strong battery to:
    1. Close the solenoid
    2. Spin the starter
    3. Engage the Bendix
    4. Provide voltage to the coil.
    As the battery gets weaker, the first thing to fail is your spark. If the battery is almost totally dead, all you will hear is the solenoid clicking.
    The more current you use to spin the starter, the less you have for the ignition.
    Always get a good brand battery – DEKA, INTERSTATE, EAST PENN/DURACELL, EXIDE, are the best. Low budget ones tend to have poor lifespans so you end up buying a new one every few years. A 6V is a GRP 1 type and a 12V uses the GRP 25 or 35 Type. Some batteries are bad out the door of the parts store. Once everything is right with the world, you should invest in a float charger like the Battery Tender Jr to maintain a full charge when tractor is idle and when you need it.
    The second most often usual suspect of a non-starting machine is whether or not your setup is using a fan belt tension device. Without proper fan belt tension, you will never charge the battery, regardless if using a 6V system with a GEN & Cutout (or a VR with an 8N) or a 12V setup with an alternator. 12V conversion kits sold today sometimes include a belt tension bracket. Check before you buy. It matters.
    The third possible root cause of non-starting is the distributor. The FORD Front Mount is often misunderstood and can be set up wrong. Mounting the correct way is very important and if done wrong will damage the base and cause issues. Cam shaft end and Cam & Weights on unit are offset and must mate up male to female. Rebuilding the front mount is an art. It must be done with unit on your bench, cleaned, and points gapped at .015” then timed correctly. Use a good set of points such as the Standard Ignition/Blue Streak FD-6769X set, NAPA sells them. The rebuild requires ensuring the copper strip is connected correctly to the points. Replace the condenser with the new one in the kit. Some have replaced the condenser many times when problems arise thinking they have a faulty part. How do you know how to test? Never assume. The only way to verify a condenser is good or bad is with a special test machine. I can say honestly say I have never had a bad condensor. Ensure the Coil pigtail is properly making a good contact.
    Next, test with your VOM set to CONTUNUITY like this:
    1. Coil off, cap off, points open, with one probe on the brass screw and the other probe on both sides of the open points. On the side closest to the cam, you should have continuity. Not on the other side! If you do, you will also have continuity everywhere else because the points are grounded.
    2. Coil off, cap off, points open. Place one probe on the brass screw and the other anywhere on the body of the distributor. You should have no continuity! Now, rotate the tang on the distributor. As the points open & close, you should have continuity (closed) and none when they open.
    3. Put the coil on the distributor, cap off, points open. Place one probe on the lead on the top of the coil, the other on the cam side of the open points. You should have continuity!
    4. Coil on, cap off, points open. Place one probe on the lead on the top of the coil, the other anywhere on the body of the distributor. You should have NO continuity!

    When the rebuilt distributor passes timing and testing, it is ready to be mounted back on the engine. Take your VOM and measure your battery voltage and note it. On the Ballast Resistor, looking at the rear dash, there are three terminals and only the top two are active, one on either side of the resistor. The LH terminal only connects to the coil wire and the RH terminal is the Ignition Switch wire connection. That's it, nothing else wired on either side. The middle bottom terminal is only a semi-passive junction post. Take your VOM and set to VDC. Apply one probe (polarity doesn't matter) to the LH Resistor terminal - should be the coil wire. Apply the other VOM probe to metal ground anywhere. Ignition Key Switch ‘ON’ but do NOT turn engine over. You should see battery voltage with points open and about half that with points closed. You can open and close the points simply by tapping the neutral safety start pushbutton without key on. YES? So far all OK. Move a probe to the top of the coil post now and repeat. Pass? Yes? You are getting the correct V to distributor.
    Finally, your wiring is all so important to have correct no matter if 6V or 12V. If you choose to go with 12V, you can use a 1-Wire alternator or a 3-Wire unit. Use JMOR’s Pictograms for 12V to see how each is wired. Before mounting the distributor decide if you want to use the OEM 6V coil or opt to replace with a new 12V coil. With the 6V original coil on a 12V setup, you will need to also buy a 1-OHM external resistor or equivalent, and insert it in the circuit with the coil wire. Swapping out to a 12V coil will eliminate the end for an external resistor, my personal choice. In the 12V circuit, you can also decide if you want to use the OEM AMMETER or swap it out for a VOLTMETER –see PICTOGRAMS. My personal choice is to stay with the AMMETER. Think of the movie “Apollo 13”. To fix the problem, the crew had to conserve what amps were left in the batteries. They needed no more than a 20A draw in order to restart the capsule for getting back to Earth. AMPS/current are everything, not volts, a technician says. Without it they don’t fly. An AMMETER will show a current charging and that is more important than a VOLTMETER just showing what the battery voltage is reading.
    A long post but I hope to have covered all the important details on the electrical systems.

    Tim Daley(MI)

    Phillip G.    Posted 08-10-2022 at 15:50:43 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • I guess I don't understand. I'm really not afraid to ask any questions. I simply couldn't remember what Ford did not won't at the coil concerning amperage. I did in fact have a Ford N series manual that specifically stated the specs that were needed for a front mount coil. I took those specs and figured out how to drop the amperage to only 3.5 amps at the coil, it seems to me. I'm thinking the manual said they didn't won't over 4.5 amps. because it would obviously burn up the not so great coil even when their new. I've bench wired my coil to 12V battery, and I can get a spark in the open atmosphere. But, does it have spark once the coil gets hot, or put under compression as a spark plug is becomes the question. So, a bench spark becomes an inaccurate test method. I'm also showing 9 ohms of resistance with the coil un-hooked from anything. I do appreciate what you've outlined, as its great information.

    Tim Daley(MI)    Posted 08-11-2022 at 04:56:32 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • OK, I'm still at a loss as to what you are trying to accomplish. If you are having a non-starting issue with your 2N and you are using a 12V/NEG GRN setup, all the wiring needs to be verified to be correct beginning with a good battery. Tell us how you are wired. Is the Cutout Circuit removed? Have you certified the distributor is timed, tested, and mounted correctly, and hasn’t a cracked base? Are you getting spark? If you suspect you have a bad coil, try another one. Coils will burn out if the ignition key is left on with the tractor off and points closed. It can melt the insulating tar inside and thus short out when powered up. When the coil cools down, the tar can solidify and may work fine next time starting is attempted. Once the coil gets hot however it may fail again. Have you inspected it for any cracks? You say you have a 12V coil. Did you verify that or just assuming because the box it came in says so? With a 6V Coil and using a 12V system, you need to add a drop down external resistor in the coil circuit. The white ceramic 1-OHM resistor is the common one used but alternatives are twisting two, 1 OHM/10 W standard resistors together, or wiring a diode inline. In the lime-green 8N Service Manual for Dealers & Mechanics, the Electrical Spec Data Sheet is in the back –SEE PIX. The coil lists resistance of the primary and secondary windings. The primary resistance is about .5 OHMS. Your standard VOM won’t measure the 5800 OHM setting on the secondary. If coil seems to meet the static test as stated, but no spark and coil to distributor tests good, then I’d say your problem is in the distributor then.

    From Bruce(VA):
    Bottom line.......coils do go bad, but I'll venture a guess that 75% of new N coils sold today are sold to folks who do not understand how to diagnose a poor spark problem or how a coil works. So, for those who don’t know any better, in a no spark situation the first suspect is usually the coil……and, more often than not, it isn’t the problem.


    Tim Daley(MI)

    Phillip G.    Posted 08-11-2022 at 16:24:32 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • Okay, I didn't say I had a 12V coil. (I have not bought anything new). I wired this tractor some years ago after I did a 12V conversion in accordance for a 6V coil that I had already that was "new". I wired it through the cutout, then through the .5 ohm factory resistor, and then put a 2 ohm ceramic resistor inline to the coil 12V feed. The best I can remember, this achieved the 3.5/4.0 Amp maximum at the coil I was needing.

    Now, it ran fine for many years until I was laying hay down with my Ford 515 sickle, and it just quit all at once a week ago. I then began checking wiring, amp gauge, resistors, etc. and found no issues. I then proceeded to the coil and distributor, and found a bad coil & timing advance flyweights coming apart in the distributor. You're right, coils can be fine when cold but, when they are energized the winding break can separate and lose everything. I've been an automotive/diesel mechanic for 42 years. Onboard computer diagnostics technician for 27 of those. I just simply could not remember what Ford wanted at the coil concerning maximum amperage.

    Tim Daley(MI)    Posted 08-11-2022 at 17:01:11 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • Phil, yes you did! Look two posts down... "...12V battery & coil. I'm running an alternator..." Again, you REMOVE the ROUNDCAN CUTOUT from the circuit altogether when doing a 12V switcheroo job on the 9N/@N tractor. Use PICTOGRAMS by JMOR for your roadmap. I advise you get a new coil, preferably a certified 12V coil. Have you got into the distributor thoroughly? Last time you rebuilt it? If base is busted, maybe 100% of your issues. Start there, time test mount and try it.


    Phillip G.    Posted 08-11-2022 at 19:31:32 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • Hell Tim, with all the tractor projects I have going there's no telling what I'm crossing up... Lol. I did find a bad coil & flyweights on that particular tractor however.

    Tim Daley(MI)    Posted 08-12-2022 at 02:38:57 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • Hey Phil, no problem, we all get that way. At this point I want to propose that I am willing to rebuild your front mount distributor for you correctly, you pay for parts and shipping. Be sure you have the OEM Ballast Resistor in the circuit and discard any other external resistor with using the 12V coil. It will be your responsibility to get it mounted correctly on the engine and wired correctly with a 12V coil. Get a good, fully tested and charged battery too. Use your 12V ALT and be sure it has belt tensioner device attached. Put your VOM and OHM meter aside for now and forget about trying to measure anything except when testing the distributor, coil voltage, and doing a spark test. Email me if interested...

    Tim Daley(MI)

    JMOR    Posted 08-09-2022 at 14:07:18 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • Are you wanting to run 6v or 12v battery? 6v or 12v coil?

    Phillip G.    Posted 08-09-2022 at 15:02:37 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • 12V battery & coil. I'm running an alternator.

    Phillip G.    Posted 08-09-2022 at 14:59:55 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • 12V battery & coil. I've converted it to 12V years ago, and I'm running an alternator.

    JMOR    Posted 08-09-2022 at 15:15:37 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • So, all is well? What is the question(s)?

    Phillip G.    Posted 08-09-2022 at 15:30:41 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • I just can't remember what the maximum & minimum ohms, and or amps should be at the coil that I figured out when I did the 12V conversion. I have an inline porcelain resistor in addition to the factory resistor behind the dash, so I must have wired that for a 6V coil at the time.

    JMOR    Posted 08-09-2022 at 17:04:07 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • Factory 6v (runs about 7.2 charging) had a coil ranging from about 1.0 to 1.5 Ohms (not real tight tolerances) and a dash mounted 3 terminal block containing a temperature dependent resistor that was around 0.3 Ohms room temp & 1.3 to maybe 1.7 RED HOT, and typically running conditions was about 0.5 Ohms. So, 7.2/(1+0.5)=4.8A and if coil 1.5 Ohms, 7.2/2.0=3.6A. The temperature dependent function allowed for some limiting/adjustment/variation/etc. Now, if converted to 12v system (running 14.4v) and keep 6v coil, dash mounted resistor, then current would be 14.4/(1.0+0.5)=9.6A... killing such coil! So along comes the white ceramic resistor of anything from 1.0, 1.2, 1.3, 1.4, 1.6, 1.8, and some even as high as 2.5 Ohms. Makes these a gamble unless you know what you have either by part number or good accurate measurement.

    Let us look at 1.3 & the 0.5 dash & the 1.0 coil. 14.4/(1.3+0.5+1.0)=5.1A. Up the ceramic to 1.6 & then 14.4/(1.6+0.5+1.0)=4.6A. And if coil is 1.5, then 14.4/)1.6+0.5+1.5)=4A. So, here we are in ball park of original system currents.
    Before each cylinder had its own coil many/most cars & trucks ran about 14.4/3.25=4.4A, but those round can metal coils were more robust than the front mount coils and no doubt better quality insulation construction than today's Chinese imports.
    If use a "12v advertised" front mount coil of 2.5 Ohms, your current will be too high, at 14.4/2.5)=5.76A, so most conversions leave the dash mounted #12250 resistor in place and end up with a current of about 14.4/(2.5+0.5)=4.8A.

    If whatever you are using works well, I would leave it alone and file all this where ever you like. If is ain't broke don't fix it!

    Phillip G.    Posted 08-09-2022 at 19:10:52 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • By gosh, I believe that was it. I did use the dash resistor and I think a 2.5 ohm ceramic resistor because I figured out I didn't won't but 3.5 to 4 amps at the coil. I had this in a manual when I did it some 10 years ago. The coil has gone bad I'm fairly certain. It's showing 9 ohms of resistance with it un-hooked. I'll do some further testing because the timing advance flyweights have came apart also. I may just do some research on those aftermarket distributors & a 12V coil. I believe you have given me the same specs I figured out when I did the 12V conversion, and I appreciate your help greatly.

    JMOR    Posted 08-09-2022 at 19:17:41 [URL] [DELETE]        [Reply] [Email]  
  • Re: Ford 2N Ignition Coil Circuit
  • Glad I could be of help.

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