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Subject: Key switch short ?

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Pete Nelson    Posted 02-17-2019 at 11:11:22 [URL] [DELETE]        [Reply] [Email]  
  • Key switch short ?
  • I have an 8N, front mounted. Started great, then died out after about 15-20 seconds. The wires from the key switch smoked - insulation melted. Replaced switch with new one, same thing happened. Scary. Starter works, ignition works, battery good. I'm guessing the smaller wires on the key switch are the weak link in the electrical system, and the trouble is elsewhere. Can't find the trouble, can't plow the snow. Need Help ! Thanks.

    Pete Nelson    Posted 03-01-2019 at 15:27:55 [URL] [DELETE]        [Reply] [Email]  
  • fixed it
  • Replaced the voltage regulator, and while I was at it replaced the resistor. Starts and runs great, all fixed.
    BTW - last fall installed a block heather, which is a very good thing to do Downeast. All parts from Derek at
    " Just8N's "

    Tim Daley(MI)    Posted 02-18-2019 at 06:28:02 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Key switch short ?
  • I suspect there is something else not wired correctly. Switch wires melting would be the first clue. The ballast resistor is supposed to get hot; red hot is not normal. A new resistor will smoke when first applied with power. That is normal and is just the coating on the ceramic burning off and will cease after a minute or so. Do you have any manuals or JMOR's WIRING PICTOGRAMS? It's essential to have them all and just as important as any wrench. Note diagrams show OEM color coded wires -yours may vary significantly so never use colors as a guide. The ignition key switch is wired with one wire to the RH terminal post (as viewed from the front of tractor) on the Ballast Resistor and the other wire to the bottom terminal post junction post. Firing order is 1, 2, 4, 3 -note distributor with #1 being at the front of tractor.

    FORD 8N OEM WIRING DIAGRAMS:


    THREE CAUSES OF ACCIDENTS:


    Tim Daley(MI)

    Rusty 2N    Posted 02-17-2019 at 13:16:03 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Key switch short ?
  • By pass the key switch, see what happens.

    Jack - Iowa    Posted 02-17-2019 at 11:54:07 [URL] [DELETE]        [Reply] [Email]  
  • Re: Key switch short ?
  • Sounds as if you have a short in your wiring. According to JMOR's diagrams the wire from the switch should go directly to the ballast resistor.

    Short may be beyond the ballast in which case it should get very hot. Probably visibly.

    Link below is to those diagrams. You're should be the third diagram.

    Good Luck,

    Jack

    Wayne,Az    Posted 02-17-2019 at 15:15:16 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Key switch short ?
  • I had same thing happen 6 weeks back..48-8n-6volt,all stock..Ran great the day before..Went to start and no pop right off,,smelled smoke or ?? looked under hood and resistor was glowing,,then wire on it flamed..My pos(ground) side atatched with marine type wing nut,,got it off and heat stopped..looked all over and decided the resistor had died/shorted after only 70 years.called just 8ns and got new switch,,ammeter,,and resistor with new insulator block..replaced parts and all burned wires and running fine a month later.. H.T.H

    Jack - Iowa    Posted 02-17-2019 at 18:38:42 [URL] [DELETE]        [Reply] [Email]  
  • Re: Key switch short ?
  • Having a wire wound resistor short is weird! That is not saying it cannot happen as you have proved. After almost 70 years in electronics, almost anything is possible.
    '48 was a good year! I graduated high school!

    Jack

    Pete Nelson    Posted 02-17-2019 at 15:40:59 [URL] [DELETE]        [Reply] [Email]  
  • Re: Key switch short ?
  • Wayne: Thanks for this. The only thing I could think of next was to replace the resistor and block, and another switch, and try it again. It's operated fine for 2 years, so everything is wired correctly. The resistor is old, maybe original. What burned was the insulation of the 2 switch wires. Sitting there with smoke erupting from behind the gas tank somehow makes me nervous !

    Jack - Iowa    Posted 02-18-2019 at 09:41:14 [URL] [DELETE]        [Reply] [Email]  
  • Re: Key switch short ?
  • Pete,

    I forgot about the center terminal on your ballast resistor block. It is only a terminal spot and should not be a part of your problem. If you take the wires off of it, be sure and keep them all together.

    Jack

    Jack - Iowa    Posted 02-18-2019 at 09:02:05 [URL] [DELETE]        [Reply] [Email]  
  • Re: Key switch short ?
  • Pete,

    Possibly you are somewhere, where a store is not readily available.

    I suggest you remove all wires from the ballast resistor except the one from the switch. Should only be one, going to the coil. Once you have done that, turn the switch on and see if the resistor still gets hot. If it does you will have to replace it. If there are more than one wire you will need to determine where they go.

    If it does not get hot, reinstall the wire which comes from the coil and see if it now gets hot. If it does, disconnect the wire from the coil and repeat the test.

    Post back what you find.

    Good Luck,

    Jack

    Jack - Iowa    Posted 02-18-2019 at 08:39:37 [URL] [DELETE]        [Reply] [Email]  
  • Re: Key switch short ?
  • Pete,

    It's time for troubleshooting. You may stumble on the problem by continuing with parts changing but likely faster and certainly cheaper to troubleshoot and find the problem.

    Do you have a meter? One that reads Ohms? You can pick one up for less than $20.

    Not promoting any vendor but here is one which would do the job.

    Plenty of help available for you to learn how to use it.

    Good Luck,

    Jack

    Tim Daley(MI)    Posted 02-18-2019 at 08:18:18 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Key switch short ?
  • Nope. "...operated fine for 2 years...so everything is wired correctly." Don't assume anything. Verify things. So why did you replace the harness? Old and frayed wires would be a good reason but all of your frying wire issues began when you did that. Speaks volumes. You can keep burning up switches and possibly other things until the true root cause is determined. Just replacing parts isn't a logical approach. Again, for the last time, you have something incorrect in your wiring. We've given you all the documents you need to get going troubleshooting. Until you do as we suggested, there's nothing more we can help you with.

    Tim Daley(MI)

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