Page 1 of 2 12 LastLast
Results 1 to 10 of 12
  1. #1
    Member
    Join Date
    Apr 2011
    Posts
    40
    Tractor
    1959 Ford 641, 2011 Kubota M6040

    Default Ford 8N Ignition and Resistor

    Hello all,

    I have a question regarding my 1949 Ford 8N tractor. It has been converted to a 12V system (before I purchased it). It's haveing some trouble starting now--no spark, and as I look over the system, I notice that the coil says "External resistor required". However, the supply wire to the coil goes straight to the ignition switch--no resistor in the path. There is a resistor mounted forward of the distributor, but it's not connected to anything.

    Will this be a problem? (The tractor has run fine most of the time for the year that I've had it, in spite of this).

    Thanks!

    -Jack

  2. #2
    Veteran Member whodat526's Avatar
    Join Date
    Apr 2010
    Posts
    1,529
    Location
    deridder louisiana
    Tractor
    fords

    Default Re: Ford 8N Ignition and Resistor

    Quote Originally Posted by jpsheb View Post
    Hello all,

    I have a question regarding my 1949 Ford 8N tractor. It has been converted to a 12V system (before I purchased it). It's haveing some trouble starting now--no spark, and as I look over the system, I notice that the coil says "External resistor required". However, the supply wire to the coil goes straight to the ignition switch--no resistor in the path. There is a resistor mounted forward of the distributor, but it's not connected to anything.

    Will this be a problem? (The tractor has run fine most of the time for the year that I've had it, in spite of this).

    Thanks!

    -Jack
    yes it will cause the coil to burn out u either need a resitor or a coil with the internal resitor

  3. #3
    New Member
    Join Date
    Mar 2011
    Posts
    9
    Tractor
    kubota bx25

    Default Re: Ford 8N Ignition and Resistor

    I have an 8N that is converted to 12v. I have a resistor before the 6v coil and have no problems. However, there are 12v coils available for the front mounted distributors of the early 8N's.

  4. #4
    Veteran Member whodat526's Avatar
    Join Date
    Apr 2010
    Posts
    1,529
    Location
    deridder louisiana
    Tractor
    fords

    Default Re: Ford 8N Ignition and Resistor

    u still need a resistor unless the coil has printed on it that it as a internal resistor

  5. #5
    Member
    Join Date
    Apr 2011
    Posts
    40
    Tractor
    1959 Ford 641, 2011 Kubota M6040

    Default Re: Ford 8N Ignition and Resistor

    Thanks for the info. It looks like it has a resistor, mounted just forward of the distributor. But it is hooked to nothing! What configuration to I hook to the resistor to the coil in? (does it just go in series between the positive side of the coil and the starter switch?

    I'd really like to post photos (worth a thousand words), but the posting feature only allows a URL. Is there a way to upload photos and attach them to posts like this?

    Thanks again!

  6. #6
    Veteran Member whodat526's Avatar
    Join Date
    Apr 2010
    Posts
    1,529
    Location
    deridder louisiana
    Tractor
    fords

    Default Re: Ford 8N Ignition and Resistor

    yes the resistor goes between the switch and the coil

  7. #7
    Gold Member
    Join Date
    Apr 2011
    Posts
    453
    Tractor
    John Deere 2720

    Default Re: Ford 8N Ignition and Resistor

    Quote Originally Posted by jpsheb View Post
    I'd really like to post photos (worth a thousand words), but the posting feature only allows a URL. Is there a way to upload photos and attach them to posts like this?

    Thanks again!
    When you post your reply, choose the "insert image" icon and then scroll down the page to the "additional options" section and you will see the "manage attachments" button. Click the button and it will then allow you to insert photos directly. There is a size limit so you may need to scale-down the size of the image beforehand.

    - John

  8. #8
    Old Timer Soundguy's Avatar
    Join Date
    Mar 2002
    Posts
    51,530
    Location
    Central florida
    Tractor
    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: Ford 8N Ignition and Resistor

    just to be clear on a few things.

    the front mount coils have a single terminal, and the side mounts have 2.

    it is possible to gut a front mount coil, and run wires out of it and use a round coil.

    you can get round coils for 12v that don't need a external resistor.. the napa IC14SB

    the 12v marked front coils STILL need a resistor.. their impeadance is only 2.5 ohms, and was meant to be run in tandem with the oem ballast resistor back on the dash.

    as for 'internal resistor' coil terminology.. that is archaic. you will be hard pressed to buy a modern made ignition coil today that atually includes a resistive element, vs just have the correct number of turns of primary and secondary wire, of the correct diameter to make up its primary and secondary impeadance.

    running on 12v with to low a value coil leads to reduced breaker life and coil life, and thus weak or no sparks, and thus, bad running and hard starting as the points surface area arcs, pits and erodes faster than designed, and the coil primary insulation potting melts and allows thermal damage between windings and then you start getting shorted turns. as more turns short, current goes up and resistance goes down heat goes up.. it causes a cascade effect... round coils.. at least modern ones are oil filled and disipate heat much more efficiently than the older front mount, square oem tar potted ones, or the newer epoxy potted ones.

    soundguy

  9. #9
    Member
    Join Date
    Apr 2011
    Posts
    40
    Tractor
    1959 Ford 641, 2011 Kubota M6040

    Default Re: Ford 8N Ignition and Resistor

    Ok, in my greenhorn ignorance, I thought my tractor was an 8n. It was actually a 641! (I did not grow up with tractors and don't know many people with them, so I'm having to teach myself).

    Update: I replaced the coil with aone with an internal resistor. I also replaced the plugs (w/ hotter ones), point, and caps. Now, it starts with no problem. Still diesels, but that's a different problem!

  10. #10
    Old Timer Soundguy's Avatar
    Join Date
    Mar 2002
    Posts
    51,530
    Location
    Central florida
    Tractor
    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: Ford 8N Ignition and Resistor

    is it dieseling.. or is it running on due to no ignition isolation?

    soundguy

Page 1 of 2 12 LastLast

Similar Threads

  1. Just bought an 8N
    By Mopar92 in forum New Holland Owning/Operating
    Replies: 30
    Last Post: 09-12-2013, 06:48 PM
  2. 8N no spark
    By BigDanT in forum Ford Vintage Tractors
    Replies: 7
    Last Post: 04-19-2011, 08:03 PM
  3. 8N Ford coils
    By pat32rf in forum Parts/Repairs
    Replies: 12
    Last Post: 12-23-2009, 10:45 AM
  4. 8N will not start
    By Chuck1949 in forum Ford Vintage Tractors
    Replies: 4
    Last Post: 10-16-2008, 02:35 PM
  5. Jump-Starting a Ford 801
    By Mrwurm in forum Ford Vintage Tractors
    Replies: 3
    Last Post: 12-02-2003, 10:11 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
© 2016 TractorByNet.com. TractorByNet is a registered trademark of IMC Digital Universe, Inc. Other trademarks on this page are the property of their respective owners.