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Subject: 1940 9N no spark

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Luke    Posted 06-14-2017 at 09:54:18 [URL] [DELETE]        [Reply] [Email]  
  • 1940 9N no spark
  • I have a 1940 Ford 9N. I have a front mount single wire 6v coil on a 12v system and 12v single wire alternator. My question is: Do I need to go through a 12v to 6v ignition resistor and also the white ceramic ballast resistor before going to the 6v coil? Any help would be greatly appreciated. Thanks

    Rustyal    Posted 06-15-2017 at 17:41:51 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 1940 9N no spark
  • I purchased a 1 wire alternator and the resistor (big white resistor) came with the one wire alternator. I have noticed the open wire resistors rust quickly on a tractor. And the one wire alternator didn't last either.

    JMOR    Posted 06-14-2017 at 11:50:05 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 1940 9N no spark
  • It is simple, yet it is not. You want the right combination of resistors & coil primary resistance so as to yield 4.5 +/-0.5 amperes of steady state current. You can not just buy a 12/6 dropping resistor or any white ceramic resistor, because almost none sold are of a known resistance. Any fixed resistor that drops 6v at a specific current will drop twice as much voltage at twice the current and half the voltage at half the current. Furthermore, the coil primary resistance for a front mount coil can vary by 3:1 over the spread of makers and time. If you are able to accurately (& not easy) determine coil primary resistance, then it isn't difficult to calculate the additional resistance needed. Finding that value is also a problem, because auto supply stores typically don't know the resistance of what they are selling. Tractor mail order sites commonly sell the 8NE10306 & depending on source & when purchased, they vary by 3:1 (terrible!). I take a good Ohmmeter to their counter & have them bring out what they have.

    Luke    Posted 06-14-2017 at 12:35:27 [URL] [DELETE]        [Reply] [Email]  
  • Re: 1940 9N no spark
  • JMOR, how do I determine the resistance of my 6v coil? It's got a metal spring and a metal piece sticking out of it. Do I read the resistance (ohms) across the two?

    Tim Daley(MI)    Posted 06-14-2017 at 12:56:24 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 1940 9N no spark
  • Not JMOR, but you want to set your VOLT/OHM METER to (Ω) OHMS, and measure from the screw stud on top (where the wire fastens)to the pigtail spring on the bottom. Polarity isn't a factor. The resistance on a 6 volt coil should be about 1.5 Ω static, meaning no charge applied. Also, look in our HOW-TOs under ELECTRICAL for JMOR's wiring pictograms for all the correct ways to wire these N's...
    LINK at bottom-

    JMOR    Posted 06-14-2017 at 12:48:20 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 1940 9N no spark
  • Measure between the bottom pig tail coil spring & the screw on top. It should be between 0.5 Ohms and 1.5 Ohms. Check meter by holding both leads together first. It is not easy to read such low values accurately & repeatedly.

    Luke    Posted 06-15-2017 at 06:14:16 [URL] [DELETE]        [Reply] [Email]  
  • Re: 1940 9N no spark
  • Last Nights findings:
    6v coil has 1 ohm resistance
    ballast resistor has 6 ohms resistance
    I have no clue where to go next.
    Thanks for all your help so far.

    Luke    Posted 06-14-2017 at 14:26:46 [URL] [DELETE]        [Reply] [Email]  
  • Re: 1940 9N no spark
  • Would it make life any easier to just put a 12volt coil on the tractor?

    HCooke    Posted 06-14-2017 at 15:07:12 [URL] [DELETE]        [Reply] [Email]  
  • Re: 1940 9N no spark
  • Then you would just need the original ballast resistor and no an addition resistor.

    JMOR    Posted 06-14-2017 at 15:39:57 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 1940 9N no spark
  • Thanks, I have been away for awhile.

    Luke    Posted 06-15-2017 at 08:28:13 [URL] [DELETE]        [Reply] [Email]  
  • Re: 1940 9N no spark
  • Took a meter and read resistance. The ballast resistor was 6 ohms and the 6v coil was 1 ohm. I'm wondering where do I go from here. Thanks for all your help!

    JMOR    Posted 06-15-2017 at 12:06:56 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 1940 9N no spark
  • It probably won't even start/run with that 6 Ohm resistor....too large. A good starting point is about 2 Ohms, perhaps the ICR-13SB or Delco D-1106, both are 1.82 Ohms,

    Luke    Posted 06-17-2017 at 09:05:47 [URL] [DELETE]        [Reply] [Email]  
  • Re: 1940 9N no spark
  • The tractor fired right up! Thanks you for the info JMOR!

    JMOR    Posted 06-17-2017 at 09:52:43 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 1940 9N no spark
  • You are very welcome!

    Luke    Posted 06-15-2017 at 12:55:48 [URL] [DELETE]        [Reply] [Email]  
  • Re: 1940 9N no spark
  • I will sure give it a shot. Thank you so for your help!

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