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!
- Thread starter bobgrimes
- Start date
Bruce (VA)
Well-known Member
grandpa Love
Well-known Member
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.
Bruce (VA)
Well-known Member
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.
75 Tips
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.
75 Tips
grandpa Love
Well-known Member
I have 3 Ns all front distributor.....
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...
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...
grandpa Love
Well-known Member
Huh? Extra resistor? Original
resistor? Help? What's the
difference? Where do these things
go? Thanks
resistor? Help? What's the
difference? Where do these things
go? Thanks
Bruce (VA)
Well-known Member
grandpa Love
Well-known Member
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!
Bruce (VA)
Well-known Member
grandpa Love
Well-known Member
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.
Similar threads
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.
Copyright © 1997-2024 Yesterday's Tractor Co.
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy