Yesterday's Tractor Co. Shop Now
   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver
Classified Ads
Photo Ads
Tractor Parts

Discussion Forums
Project Journals
Tractor Town
Your Stories
Show & Pull Guide
Events Calendar
Hauling Schedule

Tractor Photos
Implement Photos
Vintage Photos
Help Identify
Parts & Pieces
Stuck & Troubled
Vintage Ads
Community Album
Photo Ad Archives

Research & Info
Tractor Registry
Tip of the Day
Safety Cartoons
Tractor Values
Serial Numbers
Tune-Up Guide
Paint Codes
List Prices
Production Nbrs
Tune-Up Specs
Torque Values
3-Point Specs

Tractor Games
Just For Kids
Virtual Show
Museum Guide
Memorial Page
Feedback Form

Yesterday's Tractors Facebook Page

Related Sites
Tractor Shed
Ford 8N/9N Club
Today's Tractors
Garden Tractors
Classic Trucks
Kountry Life
John Deere Tractors Discussion Forum
Show Parts for Model:

Re: 70 ign problem update

[Show Entire Topic]  

Welcome Guest, Log in or Register
Author  [Modern View]
John T

11-18-2013 13:17:25

Report to Moderator

"i thought the resistor was to keep the points from burning up. will it also cause the coil to go bad?"

The ballast resistor is there to drop coil voltage (from 12 down to 6) and reduce coil current (from say 8 without down to acceptable 4 amps with resistor). If its a 12 volt tractor with a 6 volt coil and theres no resistor, the coil will overheat PLUS the points will burn up prematurely........

John T

[Log in to Reply]   [No Email]
Bob Harvey

11-18-2013 14:37:46

Report to Moderator
 Re: 70 ign problem update in reply to John T, 11-18-2013 13:17:25  
My understanding of a 'Ballast Resistor' is: they are used to vary the resistance by the influx of heat. To make more sense, when the resistor is cool, almost all of the 6v goes through to power the points system with as much juice available. As the electron keep flowing through the wire coil of the resistor, the coil heats up, reducing the energy to the points system, primarily to lower the power input to the coil, thus reducing heat to the coil. (mostly for longevity I suspect)

[Log in to Reply]  [No Email]
John T

11-18-2013 15:12:53

Report to Moderator
 Re: 70 ign problem update in reply to Bob Harvey, 11-18-2013 14:37:46  
While that has some truth for all resistors since resistance increases upon warm up, what you describe reminds me more of a THERMISTOR. A typical old tractor ballast is more like 1.25 to under 2 ohms fixed, although sure it would be somewhat less when its cold. Its primary purpose is to drop 12 tractor volts down to 6 when using a 6 volt coil while the limited thermal characteristics can indeed improve cold weather starting

Fun chat

John T

[Log in to Reply]  [No Email]
Bob Harvey

11-18-2013 16:22:18

Report to Moderator
 Re: 70 ign problem update in reply to John T, 11-18-2013 15:12:53  
Beg to differ. A 'reducing' resistor does just that with in a second or less, a 'Ballast Resistor' slows down the process with the use of a longer (lengthwise) wire coil, hence a slower response to the loss of energy that goes to the starting system = more juice to the coil/points system during starting. Seems to me the # series had that system hard wired into the "Ignition switch".

[Log in to Reply]  [No Email]
John T

11-18-2013 16:32:40

Report to Moderator
 Re: 70 ign problem update in reply to Bob Harvey, 11-18-2013 16:22:18  
Yep I think the 720 etc had the stand alone discrete white ceramic bathtub style of ballast resistors while the new generation had more like a wire link or fusible link looking thermistor on the ignition switch that acted more like the resistor/thermistors you described. My answer covers the old style two cylinder tractors with more of a fixed resistance voltage dropping current reducing ballast which isn't the same as what you're describing. I think youre more right for new generation and Im more right for the old two cylinder tractors.

Very fun chattin with ya, thanks for the info

John T

[Log in to Reply]  [No Email]
Bob Harvey

11-18-2013 16:48:40

Report to Moderator
 Re: 70 ign problem update in reply to John T, 11-18-2013 16:32:40  
Right back at ya. My limited knowledge of the subject is based on the 2 'N' Ford's I had. My '60' has a resistor as part of the 'ignition' sw., but I think it has to do with the lights.

[Log in to Reply]  [No Email]
John T

11-19-2013 05:05:01

Report to Moderator
 Re: 70 ign problem update in reply to Bob Harvey, 11-18-2013 16:48:40  
Youre right, many brands of tractors with that wire coil resistor on the ign/light switch THATS A LIGHT DIMMING RESISTOR.

Many other tractor light/ign switches have TWO RESISTORS on the switch. One (flat wound) is the generators field current limiting resistor for Low or High charge on tractors that used a cutout relay NOT a Voltage Regulator and the other coil of wire/resistor is for light dimming.

The older two cylinder Deeres (720 etc) used a stand alone discrete fixed bathtub style ballast ignition resistor and and a start by pass system so the coil got battery voltage while cranking but reduced (6 volt) when running.

Some of the 12 volt New Generation Deeres (that used a 6 volt coil) had a thermistor/resistor type device on the switch or wired to it (looks like a wire fuse link etc) AND THERE WAS NOOOOOOOOOO START BY PASS NEEDED because the resistance was low for starting but when it warmed up its resistance increased so the coil only saw 6 instead of the closer to 12 volts at starting. I THINK THATS THE TYPE OF DEVICE YOU ARE THINKING OF

Whewwwwwwwwww got all that lol post back an questions

John T

[Log in to Reply]  [No Email]
[Show Entire Topic]     [Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:

Fast Shipping!  Most of our stocked parts ship within 24 hours (M-Th). Expedited shipping available, just call! Most prices for parts and manuals are below our competitors. Compare our super low shipping rates! We have the parts you need to repair your tractor. We are a company you can trust and have generous return policies. Shop Online Today or call our friendly sales staff toll free (800) 853-2651. [ About Us ]

Home  |  Forums

Copyright © 1997-2018 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