Farm Equipment - Battery Connectors

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Battery Connectors

Printed From: Unofficial Allis
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=161361
Printed Date: 29 May 2025 at 12:59am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: Battery Connectors

Posted By: Geo47
Subject: Battery Connectors
Date Posted: 27 May 2019 at 8:02am

I bought an Allis Chalmers C at an auction. From the serial number, it appears to have been built in 1947. When I got it home, I bought a new 6 volt battery. I was unaware that this tractor was probably a positive ground until later. When I disconnected the old battery, I didn't take note as to how it was connected. When I went to connect the new battery, the ground connector would not fit on the positive post of the battery (the positive post is larger diameter than the negative post). This led me to question whether or not this tractor is actually positive ground or maybe has been changed. Does anyone know how to determine which it is?

Thanks

George

Replies:

Posted By: Gerald J.
Date Posted: 27 May 2019 at 9:18am

Check the ignition coil polarity connection. If positive ground the + terminal on the coil goes to the distributor points. If negative ground the - terminal on the coil goes to the points. Then check the ammeter connections. For negative ground the - terminal goes to the battery and the + terminal goes to the generator. For positive ground the + terminal goes to the battery and the - terminal goes to the generator.

For one more check, hand crank it without the battery and check the polarity of the generator voltage if you can get it to run.

The fits of the cables to the battery posts are a hint of the polarity the different sizes of the posts is there to help you get the battery polarity to match the system polarity.

If the ignition is magneto, its independent of the battery polarity.

Gerald J.

Posted By: Geo47
Date Posted: 27 May 2019 at 11:20am

Thanks Gerald. I am assuming since my C has a magneto, I can't check the polarity on the coil. I will check the ammeter connections to see if I can tell from that. I haven't yet been able to start the tractor. I just replaced the magneto with a rebuilt unit as it was not firing. Not sure I have the timing right yet or maybe I have a carburetor problem. But, the polarity issue is separate from my starting problems. I'm not in town for a while so I won't be able to follow this up for a while. Thanks for your response. I will let you know what I find out when I get back to the farm.

George

Posted By: DougS
Date Posted: 27 May 2019 at 3:09pm

Hook it up the way the cables will allow. The starter doesn't care. The lights don't care. If the generator charges the battery you're good to go. Someone may have reversed the polarity once upon a time. As long as the ammeter is pointing correctly and the battery is charging, it doesn't matter.

Posted By: Geo47
Date Posted: 27 May 2019 at 4:56pm

Thanks, that clarifies things. I will do that.

George

Posted By: Gerald J.
Date Posted: 27 May 2019 at 6:04pm

If the generator polarity is opposite of the battery polarity, both the generator and the battery can be destroyed.

A simple ammeter test is to turn on the lights with the battery connected but the engine not running. The ammeter then should show discharge providing the lights aren't controlled by the generator voltage regulator. In that case borrow a headlight and connect it to the battery terminal on the voltage regulator and the ammeter should show discharge if the battery charger matches the ammeter polarity.

The destruction of the generator and battery is prevented by following the op manual instructions for flashing the generator, basically jumping the battery to armature connections on the voltage regulator to magnetize the field poles to give to generator polarity the same as the generator. Otherwise the generator and battery with opposite voltages are completely shorted and that is hard on them and the wiring between them including the voltage regulator cutout section.

Gerald J.

Posted By: Geo47
Date Posted: 28 May 2019 at 8:10am

Thanks Gerald, I appreciate the information. unfortunately, the tractor has no lights and I don't have an ops manual. Additionally, my understanding of electrical systems is probably less than adequate. However, I think I can noodle through this given your information. How can one get an ops manual?

Thanks,

George

Posted By: CTuckerNWIL
Date Posted: 28 May 2019 at 8:18am

Hook the battery up the way the cables fit. Then, before starting it, temporarily flash battery voltage to the field terminal on the generator a couple times. Then you are good to go with no problems. You could also just disconnect the generator before cranking it over or running it and have no problem.

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http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com
Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF

Posted By: Geo47
Date Posted: 28 May 2019 at 9:14am

Sounds simple enough.

George

Posted By: Gerald J.
Date Posted: 28 May 2019 at 9:20am

Don't flash the field terminal flash the armature terminal.

I have found some manuals at:
http://grandpas-tractor-site.s3.amazonaws.com/manuals/ac" rel="nofollow - http://grandpas-tractor-site.s3.amazonaws.com/manuals/ac

The shop manual that I have at:
http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf" rel="nofollow - http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf
has the wiring diagram. I'm sure it was shipped positive ground.

Gerald J.

Posted By: Geo47
Date Posted: 28 May 2019 at 9:46am

I agree it was shipped positive ground. It has a diagram on the back of the battery box that shows it. But, the battery connectors don't fit that way.

The Grandpas tractor link doesn't seem to work for me. I found the manual from your post. It has a photo of of a generator showing the field post, but I am unsure of where the armature post is.

Just so I am totally sure, flashing means to touch the negative post to the generator (positive ground) or touch the positive post to the generator (negative ground). Do I have that correct?

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George

Posted By: HoughMade
Date Posted: 28 May 2019 at 10:24am

After replacing the battery, especially after it sitting without a battery or with a completely dead battery if it did, you should flash the generator anyway to be safe.

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1951 B

Posted By: Gerald J.
Date Posted: 28 May 2019 at 10:02pm

Yes negative battery post to the generator armature post for positive ground, positive battery post to the generator armature for negative ground. Simpler to jump from the battery terminal on the regulator to the armature post on the generator, same for either polarity.

The generator armature post should have a wire to the A terminal on the voltage regulator or cutout if it has a 3 brush generator.

Gerald J.

Posted By: Geo47
Date Posted: 29 May 2019 at 8:06am

Thanks for all the assistance. I really appreciate it.

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George