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Ford 8N will not start with new 12v coil


 
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Satohbill
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Joined: 08 Nov 2016
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PostPosted: Thu Oct 11, 2018 7:53 am    Post subject: Ford 8N will not start with new 12v coil Reply to specific post Reply with quote

So I have a Ford 8N with with front mount coil. The other day I was in my Garden and the tractor started acting like it was starving for power. I thought maybe my coil was wearing out so I put the old 6v coil that was on it before I converted it to 12 volt and it ran fine.I ordered a new 12 volt coil and when it came in I slapped it on and the tractor would not even fire. I put the 6v coil back on and it fired right up. Replaced the ?? defective 12 volt coil with a new one and same thing. No fire. I am currently running my 8n on what I think is a 6 volt coil. Why will these 12v coils not fire on my converted system. And yes I do have the white resistor mounted on the side of my tractor. Any body got any ideas why??
 
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R Geiger
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Location: Banks, Oregon

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PostPosted: Thu Oct 11, 2018 8:06 am    Post subject: Re: Ford 8N will not start with new 12v coil Reply to specific post Reply with quote

With a 12 volt coil the only resistor you need is the original ballast resistor behind the dash.
 
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JMOR
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PostPosted: Thu Oct 11, 2018 8:13 am    Post subject: Re: Ford 8N will not start with new 12v coil Reply to specific post Reply with quote

R Geiger wrote:
(quoted from post at 12:06:06 10/11/1Cool With a 12 volt coil the only resistor you need is the original ballast resistor behind the dash.
yep, too much resistance means too little coil current = weak spark.
 
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HCooke
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PostPosted: Fri Oct 12, 2018 4:27 am    Post subject: Re: Ford 8N will not start with new 12v coil Reply to specific post Reply with quote

Remove the white resistor!
 
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Satohbill
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PostPosted: Mon Oct 15, 2018 3:04 am    Post subject: Re: Ford 8N will not start with new 12v coil Reply to specific post Reply with quote

So is that telling that the first 12 volt coil that I put on my tractor was really a 6 volt coil? How long will the 6 volt coil run with the 12 volt system?
 
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Bruce (VA)
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PostPosted: Mon Oct 15, 2018 3:16 am    Post subject: Re: Ford 8N will not start with new 12v coil Reply to specific post Reply with quote

" How long will the 6 volt coil run with the 12 volt system? "

Depends on how many actual hours of run time, the ambient temperature and the age of the coil.

Running it one hour a day for 3 months at 50* F is not the same as running it 8 hours a day at 95* F.

The problem is that overtime, heat melts the insulation inside the coil. Unless you leave the key on and the points are closed, coil failures rarely occur in 5 minutes.

Rather than guess at the coil resistance, just measure it. The Ford OEM 6v coil spec'd at 0.470 to 0.510 ohms. New 6v coils are about 1.5 ohms. 12v coils are around 2 to 2.25 ohms.

See tip # 30.

All you need is the oem ballast resistor and a 12v coil.
75 Tips

 
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HFJ
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PostPosted: Mon Oct 15, 2018 8:13 am    Post subject: Re: Ford 8N will not start with new 12v coil Reply to specific post Reply with quote

Satohbill wrote:
(quoted from post at 08:04:29 10/15/1Cool
How long will the 6 volt coil run with the 12 volt system?


i've got ~ 150 hours of moderately light duty on a 6 volt coil on my 12 volt 2N with no additional white ceramic resistor - just the OEM ballast resistor.

YMMV.
 
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