(800) 853-2651
SHOP NOW

Neg. vs. Pos. Ground

C

Clarkbug

Member
Hello All.

Im needing to appeal to all of those folks who know better than me on this one.

I bought two H's earlier this year, both all original for the most part. I got them from the second owner, who just had them for a few years and never got around to working on them.

One of them is a '45, the other a '51. They are both still 6 volt, one has a mag ignition, the other is battery ignition.

The issue is that the '45 is still hooked up positive ground, and it works great. The '51 is hooked up negative ground, but Im not sure if that is right. The ammeter swings in the reverse direction, but the tractor starts right up and runs well for the most part....

Im not sure if the '51 is supposed to be positive or negative ground. Is there an easy way to tell? Can I just hook the battery up the opposite way?

Any input anyone has is much appreciated!

~Bug
 
i think they was negative grounds when they was first out.I know i converted my case to 12 volt positve it runs good i am getting ready to start on my grandpa"s farmall a soon
jerry
 
Both of those tractors were originally positive ground. If you change the one that is currently negative ground, you will most likely need to re-polarize the charging system.
 
All six volt Farmalls and six volt most others were positive ground. Most twelve volt systems, but not all, were negative ground. Both of your tractors should be six volt positive ground.

Harold H
 

There is no "VS." about it. Positive and negative ground are simply two ways of achieving the same result.

It sounds like whoever used to own your '51 wasn't paying attention, or thought they were being smart by hooking it up negative ground. Sometimes people find the positive ground and say, "That can't be right" and switch it to negative ground.

The only difference is the direction the ammeter swings. You can fix that by switching the wires on the ammeter, too.

Both the starter and generator on a tractor this old will work just fine with positive or negative ground. Worst case is you need to repolarize the generator when you switch from one to the other.
 
6v pos gnd. The starter doesnt care which way it is but the gen does. Switching back to pos gnd wont hurt a thing but you may have to polorize gen but I dont think so because its working backwords now.
 
Dellbertt/Bug -

You MUST repolarize the generator if you switch back to positive ground. Otherwise bad things will happen to expensive electrical parts!

To repolarize simply jumper the BAT and GEN terminals at the voltage regulator for an instant. Do this after reconnecting the battery but before starting the engine...
 
If the ammeter registers just bass ackwards its cuzz polarity got swapped and the leads werent reversed as necessary to make it register correctly. Not running if light are turned on she ought to swing to - discharge but if she swings to + charge the leads need reversed. The genny will work at either polarity provided you Polarize before start up to avoid VR damage. If its a coil ignition it needs leads swapped if polarity is changed........

John T
 
Thanks for all the info everyone.

From what I gather, I can tell for sure if someone just accidentally swapped the cables on the battery by looking at the way the coil is hooked up?

If I do switch the cables back, Ill make sure to re-polarize the generator first.

Ill post back a little later with my findings. But thanks again for all the input!
 
For anyone that was keeping track, I finally got a chance today to play with the H.

It definitely just appears that the battery was switched around by the previous owner in an attempt to be helpful, and thinking that negative is always grounded.

I did try to jumper the terminals per the owners manual, but I honestly wasnt sure which was which on the generator or the voltage regulator, and none of my books helped me with that.

Im assuming on the generator that the terminal closest to the valve cover is the "a" terminal, and the one on the outside is the "f" terminal. I have the VR that is mounted to the generator, and there are three tabs. Two tabs on one side, one on the other. One of the ones on the side with two was connected directly to the generators "a" terminal, and the other was connected to the wiring harness.

There were sparks, but hopefully those werent bad sparks, but the kind I should see when re-polarizing a generator!

However, the H still runs quite rough... it starts right up, but doesnt idle very smoothly. The quest continues!

Thanks for all the help!
 
You must log in or register to reply here.

Similar threads

B
Question for pos/neg ground
Replies
10
Views
672
John Deere D
John Deere D
M
SWD9 battery ground
Replies
7
Views
353
John T
J
A
Farmall M electrical
Replies
7
Views
475
BarnyardEngineering
BarnyardEngineering
K
changing from pos to neg
2
Replies
31
Views
756
kenbob
K
L
Loston8n
2
Replies
24
Views
1K
lisamedic
L
Tractor Parts Tractor Manuals

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

Back
Top