Positive Ground ?
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Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=171414
Printed Date: 13 Apr 2026 at 3:34am
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Topic: Positive Ground ?
Posted By: FREEDGUY
Subject: Positive Ground ?
Date Posted: 23 May 2020 at 5:04pm
What was the rationale of A/C to make so many tractors over the years with this set-up? Were other manufactures of the same time doing the same? What was/is the benefit of it other than FIREWORKS hooking up a battery charger  ?
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Replies:
Posted By: jaybmiller
Date Posted: 23 May 2020 at 5:19pm
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'somethin' about batteries lasting longer or some other 'science'... basically disproven as 'everything' is negative ground for the past 5-6 decades... ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: DennisA (IL)
Date Posted: 23 May 2020 at 5:22pm
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just about everything was positive ground back in the day including cars and trucks. ------------- Thanks & God Bless Dennis |
Posted By: FREEDGUY
Date Posted: 23 May 2020 at 5:28pm
Thanks Dennis, I knew there were 6/8 volt systems "back then", but only been around the "WD/ D series" tractors  Now that I think about it, would a Gleaner "A" have been + ground ?? That's one battery I don't recall hooking up a charger/jumper cables to LOL!!
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Posted By: steve(ill)
Date Posted: 23 May 2020 at 6:22pm
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Encyclopedia .............. about EVERYTHING was positive ground befor 1960 Vehicles with "solid state" (transistorized) electronic gadgets will invariably be negative earth. The first common "solid state" electronic gadget in cars was the transistorized radio, starting in the mid 50's. Most of the early transistor car radios had a polarity plug on the back so they could be used in either positive or negative ground applications. The next common electronic gadget for cars was the triode bridge in the alternator, circa early 60's. Early alternators used silicon plate rectifiers that could be connected for either positive or negative grounding, so some early alternators were made for positive ground applications. When silicon diodes were developed with sufficient current capacity for alternator rectifiers, all alternators were quickly redesigned to use diodes. This is when all alternators became negative ground, and all cars using them were built with electrical return path connected to battery negative. ------------- Like them all, but love the "B"s. |
Posted By: DaveKamp
Date Posted: 23 May 2020 at 10:24pm
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It would be more appropriate to ask "Why did they change it". See, when vehicles first started being equipped with batteries, it was to make a more effective ignition system. They used acetylene lights, and had no electric 'self starter'. They didn't have 'impulser couplings' on magnetos... it was a direct magneto, low tension, frequently with an HT coil, or in the case of a Model T Ford, a buzzer coil powered by a permanent magnet dynamo integrated into theflywheel. When the electric self-starter was invented (google Kettering!) , he used the battery to drive a hefty, but very limited duty-cycle electric motor to provide cranking power. The concept of 'grounding' only existed for ONE REASON: Grounding uses the chassis to serve as one half of every circuit... ...so it saves lots of precious copper wire. They arbitrarily selected positive ground on MOST *but not all* cars. Why? Probably because the manufacturers were using generators and self-starters who did it that way... and while a manufacturer could choose to do it the opposite way, they just decided that it was most familiar. But when, and why did they change? That's a complicated question, with a simple answer... the rest of the automotive industry migrated that way. ------------- Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest. |
Posted By: Gerald J.
Date Posted: 24 May 2020 at 9:57am
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I have written a long post on this topic at least a couple years ago. Might still be found. Actually so long as the starter and the battery are the same either polarity works. In the 1930s vehicle and farm machinery manufacturers had individual opinions and about half used positive ground and the rest used negative ground. and the SAE standard on the topic allowed for either polarity. And also 6, 12, or 24 volts for the battery voltage. In about 1955 the SAE standard was changed to negative ground only and 12 volts only. One reason was that vehicle and tractor owners tended to not understand the effects of polarity and when jumping a weak battery from another vehicle or connecting a charger often crossed the polarity which was very hard on the weak battery and accomplished nothing in getting the engine started. So the SAE standard set 12 volts negative ground to make all modern vehicles and farm equipment all the same for owner safety when jumping or charging. Gerald J. |