Another Coil Issue?

dogtired · Jan 11, 2019

Went to start my front mount 8N after it has been sitting a spell. It is a 12 volt system. No fire to plugs. Pulled coil
and distributor. Cleaned and set points to .015. I did not check voltage before. Now. There is
voltage drop at coil. When hot wire is connected./ When hot wire to coil is not connected . Full 12
plus volts to coil./ When hot wire to coil is connected. Voltage drops to 3.0 volts at coil./Possibly a bad
coil? Running inline resistor. I accidentally touched it and it burned the crap out of my finger.
I don't know if it is a 12 or 6 volt coil. How can you tell if it is a 12 volt or 6 volt? Thanks.

Farmer Dan · Jan 12, 2019

If the points are closed that will happen. That is how folks burn up the coil. Turn the key off before you burn up your coil.

Bruce (VA) · Jan 12, 2019

" How can you tell if it is a 12 volt or 6 volt?"

Measure it w/ an ohm meter. 1.5 ohms or so on the primary (stud to pigtail) , it's 6v. 2.25 ohms or so, it's a 12v.

"I accidentally touched it and it burned the crap out of my finger. "

To get hot, the points must be closed. And to get that hot, you put full 12v battery voltage into the coil. The coil was not designed for that. See tip # 38

"Running inline resistor." Get a 12 v coil. Remove the in-line resistor. Make sure you have a working oem ballast resistor in the circuit; that's the only resistor you need. See tip # 30
75 Tips

Jim L WA · Jan 12, 2019

If the points are opening, and you are still seeing 3 volts at the top of the coil, something may be grounded in the distributor. Shorted condenser, insulator worn through, etc.

dogtired · Jan 12, 2019

OK. Call me stupid. I am used to it. What exactly is a OEM ballast resistor? I see it mentioned all the time. The resistor on mine is ceramic a couple of inches long with a spring inside. What does a OEM ballast resistor look like and where does it go? Thanks.

Royse · Jan 12, 2019

That is NOT a stupid question. The OEM ballast resistor is a wire
wound resistor mounted on the back of the dash, just below the
ammeter. It is also the place many of your wire connections are
made. Here's a picture of one from the YT parts listing.
It is essentially zero ohms cold, giving you full voltage to start your
tractor, then increases resistance when it warms up to protect your
coil. A ceramic resistor is a fixed resistance and does not provide
those benefits.

dogtired · Jan 12, 2019

Royse. Thanks. There is not that on my tractor. It has run many hours like it is until now. Could
you tell me where i can get one of those resistors without paying a arm and a leg? Thanks.

Royse · Jan 12, 2019

Unfortunately, they're not cheap. [b:cbc090d111]Here[/b:cbc090d111] they are on YT.
Your local NAPA car parts store, if you have one, can get them.
Or an internet search may turn up a cheaper alternative.
In either case, you're looking for part number A8NN12250A

Farmer Dan · Jan 13, 2019

maybe this will help. you can see the resistor on the right of the drawing.

Tim PloughNman Daley RIP · Jan 13, 2019

If you got burnt, what do you think is wrong? What would happen if a wire accidentally touched it? The wiring is mucked up for sure. Follow JMOR's wiring pictogram to a T -no shortcuts. Here is where you can get the correct 8N ballast resistor -see LINK. You can also get a 12v coil too if needed.

Tim Daley(MI)
OEM BALLAST RESISTOR FOR 8N

W_B · Jan 13, 2019

(quoted from post at 15:01:54 01/13/19 The wiring is mucked up for sure. Follow JMOR's wiring pictogram to a T -no shortcuts.

Word! Just rewired my 8N with a 12V conversion and followed the JMOR diagram exactly. It fired up first time and continues to work correctly. Not a huge deal wire it right.

Another Coil Issue?

dogtired

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Farmer Dan

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Bruce (VA)

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Jim L WA

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dogtired

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Royse

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dogtired

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Royse

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Farmer Dan

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Tim PloughNman Daley RIP

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W_B

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