Most of them are in the 1.5 to 1.8 ohm range. Typical current draw is around 3 - 4 amps, which would translate to something on the order of 20 - 25 watts dissipation. Note that these numbers are with the engine stopped and the points closed; when the engine is running, the points are open a good part of the time and the average current draw is somewhat less.
The resistance and current numbers come from an old Motor's repair manual.
Easiest approach is to go to a good auto parts store and buy a ballast resistor for a 60's or 70's vintage car. NAPA has a universal one, part number SME 185450.
By the way, the reason for cars having external resistors instead of simply using a 12 volt coil was to provide a hotter spark for starting. There would be an extra contact on either the ignition switch or starter selenoid that would bypass the resistor and apply full battery voltage to the coil for starting. Once the engine started, this contact would open, putting the resistor back in line, and reducing current through the points to a value that wouldn't destroy them quickly.
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. [ About Us ]
Today's Featured Article - An AC Model M Crawler - by Anthony West. Neil Atkins is a man in his late thirties, a mild and patient character who talks fondly of his farming heritage. He farms around a hundred and fifty acres of arable land, in a village called Southam, located just outside Leamington Spa in Warwickshire. The soil is a rich dark brown and is well looked after. unlike some areas in the midlands it is also fairly flat, broken only by hedgerows and the occasional valley and brook. A copse of wildbreaking silver birch and oak trees surround the top si
... [Read Article]
Latest Ad:
Variable pulley for case 1530 skid loader
[More Ads]
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.
