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12 volt wiring on 8n

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bobgrimes

06-28-2019 16:02:20




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I am trying to rebuild a 1948 8n. Is there some place I can find a wiring diagram for a one wire alternator. This tractor was converted from 6 volt and every thing was kind of jerry rigged. wires were glued to the old coil and ran to a conventional coil with a reducer. Front mount distributor and coil. I have purchase a new coil that mounts on the top of the distributor but the wiring diagrams I can find seem to be different than the way this was wired before. Help!

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HFJ

06-29-2019 19:02:17




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 16:02:20  
yes, the proverbial "ceramic blob" resistor is inline leading to the coil.



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bobgrimes

06-29-2019 19:28:49




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 Re: 12 volt wiring on 8n in reply to HFJ, 06-29-2019 19:02:17  
Is this in addition to the one in dash?



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HFJ

06-29-2019 18:47:34




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 16:02:20  
original resistor, resides on back of dash:



extra resistor, could be anywhere:



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JMOR

06-29-2019 09:25:36




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 16:02:20  
Quoting Removed, click Modern View to seeIf spark is strong enough for start & run, why mess with success? Maybe in the cold of winter, you will need to reduce that 4.5.



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J.Mc

06-29-2019 09:00:39




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 16:02:20  
Ok... so now I guess I have a question regarding the external resistor also. I just finished a 12v conversion on my "48" front distributor 8n. I ended up using the new external resister because I was having issues with the old ballst resister burning up my keyswitch. Yes, it was wired correctly... The new resister meters out at 4.5 ohms, so given that the new 12v coil has approx. 2ohms of resistance, that would give me 6.5 total ohms which theoretically should put me at 2.2 amps or thereabouts. Well below the 4 you mentioned. Am I correct with this? Or am I missing something that i need to go back and fix...

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JMOR

06-28-2019 20:39:45




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 16:02:20  
Quoting Removed, click Modern View to seeUnlike too many posters, if I put it out there, it is correct.



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R Geiger

06-28-2019 20:37:54




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 16:02:20  
The 12 volt coil removes the need for the extra resistor but the original ballast resistor is still required.



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Grandpa love

06-29-2019 16:40:16




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 Re: 12 volt wiring on 8n in reply to R Geiger, 06-28-2019 20:37:54  
Huh? Extra resistor? Original resistor? Help? What's the difference? Where do these things go? Thanks



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JMOR

06-28-2019 17:07:15




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 16:02:20  
Quoting Removed, click Modern View to see



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bobgrimes

06-28-2019 17:56:12




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 Re: 12 volt wiring on 8n in reply to JMOR, 06-28-2019 17:07:15  
Thanks, the old wiring had a resistor between coil and front resistor. Is this necessary?



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Bruce (VA)

06-28-2019 18:30:06




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 Re: 12 volt wiring on 8n in reply to bobgrimes, 06-28-2019 17:56:12  
Yes. You always need the oem ballast resistor with a front distributor . See tip # 30.



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Grandpa love

06-28-2019 20:03:14




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 Re: 12 volt wiring on 8n in reply to Bruce (VA), 06-28-2019 18:30:06  
Always need a ballast resistor? Even with a 12 volt coil? I thought that's why you can order 12 volt coils? I have one on the way from YT. I thought that would delete the resistor.



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Bruce (VA)

06-29-2019 03:25:00




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 Re: 12 volt wiring on 8n in reply to Grandpa love, 06-28-2019 20:03:14  
If you have a front coil (do you?) you always need the oem ballast resistor.

You need to keep the coil running current below 4 amps. As the 12v front coil usually has an internal resistance of 2 ohms, and the oem ballast resistor is 1.7 ohms hot, that gets you 3.7 ohms total resistance. 14.5 volts/3.7 ohms = 3.9 amps.

You can run it w/o the oem ballast resistor for many hours; 14.5v/2ohms is 7.25 amps, nearly twice the design parameters of the coil. Some are more robust than others, but sooner or later, you get a weak spark or no spark at all. Sorta like running low air pressure in your tires on a long trip.

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Grandpa love

06-29-2019 05:36:52




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 Re: 12 volt wiring on 8n in reply to Bruce (VA), 06-29-2019 03:25:00  
I have 3 Ns all front distributor.....



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Bruce (VA)

06-29-2019 18:49:47




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 Re: 12 volt wiring on 8n in reply to Grandpa love, 06-29-2019 05:36:52  
All three should have the oem ballast resistor installed.



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Grandpa love

06-29-2019 18:53:07




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 Re: 12 volt wiring on 8n in reply to Bruce (VA), 06-29-2019 18:49:47  
Is that the white ceramic one in between key switch and coil? I'm new to the Ns. Have owned a 640 and 960 for several years, whole different deal!



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Bruce (VA)

06-29-2019 19:06:06




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 Re: 12 volt wiring on 8n in reply to Grandpa love, 06-29-2019 18:53:07  
No.

The oem ballast resistor is on top of the terminal block. Look again. You may have 2 resistors. Which is the norm if you have a 6v coil. Do you?



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Grandpa love

06-29-2019 19:15:43




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 Re: 12 volt wiring on 8n in reply to Bruce (VA), 06-29-2019 19:06:06  
Will look tomorrow after church. Unknown coil. I ordered a 12 volt coil from YT. Actually have 2 of these I'm trying to get going. One was running,but smoking. Last week the key switch gave up, I was having to jiggle it, so to get it to drive to the barn I used a jumper wire from key switch to ceramic resistor, didn't work on one side but started on other side ( on coil side) the tractor ran about 3-4 minutes ,started running rough and back fired,then quit. Spark is really weak, barely Sparks a plug. Also has black goo oozing out if coil. We have not done any tune up to this tractor. It had been sitting for 4 years. Complete tune up has been ordered. We did change all fluids, clean carb and air breather.

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bobgrimes

06-29-2019 04:09:14




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 Re: 12 volt wiring on 8n in reply to Bruce (VA), 06-29-2019 03:25:00  
Yes, I have a front coil.



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