Farm Equipment - Flashing the GEN

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Flashing the GEN

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=191588
Printed Date: 05 Aug 2025 at 4:57pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: Flashing the GEN

Posted By: DonDittmar
Subject: Flashing the GEN
Date Posted: 02 Nov 2022 at 6:27am

OK, So after you pull an old DC generator off or have the battery unhooked for extended periods of time, you have to "flash" the GEN at the VR to get it back charging again. In technical terms, what is actually happening when you do this? Are you providing that initial residual magnetism?

All you electrical engineer guys, this is your time to shine LOL

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Experience is a fancy name for past mistakes. "Great moments are born from great opportunity"

1968 D15D,1962 D19D
Also 1965 Cub Loboy and 1958 JD 720 Diesel Pony Start

Replies:

Posted By: steve(ill)
Date Posted: 02 Nov 2022 at 9:34am

You buy a regulator that is positive or negative ground... You have to match the generator to the regulator... The generator can charge either way depending on the residual magnetism inside... With the key off, you touch the BAT and GEN or "A" terminals of the regulator to send the BAT signal to the generator.. That sets the magnetism inside so the generator knows which way to charge............... at least thats the way i was taught.

Generators should retain their magnetism when off for some period of time.. If this is a old generator or has set for months, it is a good idea to FLASH or POLARIZE .. normally do this when you get a new regulator or do bench overhaul work.

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Like them all, but love the "B"s.

Posted By: DonDittmar
Date Posted: 02 Nov 2022 at 10:49am

Thats kind of what I thought too, but I am in the process of making an educational video and I wanted to be sure before I told someone the wrong information

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Experience is a fancy name for past mistakes. "Great moments are born from great opportunity"

1968 D15D,1962 D19D
Also 1965 Cub Loboy and 1958 JD 720 Diesel Pony Start

Posted By: Flyer
Date Posted: 02 Nov 2022 at 2:02pm

A generator that has been used recently will have enough residual magnetism in the armature to initiate voltage output when the generator starts rotating. I think the term is "remanence". A generator that has been off for an extended period (or has never been in service) will no longer have enough magnetism to start the process so it has to be initiated from an external source.

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An optimist sees the glass as half full. The pessimist sees the glass as half empty. The engineer sees a glass with double the required capacity.

Posted By: Les Kerf
Date Posted: 02 Nov 2022 at 3:35pm

Yup. Flashing the generator does two things: it establishes the residual magnetism, and also establishes the polarity of the residual magnetism.

I was just a lad back in the 1960's and I clearly recall my Dad and other adult men voicing their distrust of those newfangled alternators because you could not push-start a dead battery vehicle equipped with an alternator like you could a vehicle that had a generator.

Posted By: mdm1
Date Posted: 02 Nov 2022 at 4:06pm

I remember it by Boy to Girl but never to Female! Now if I could remember key off.

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Everything is impossible until someone does it! WD45-trip loader 1947 c w/woods belly mower, 1939 B, #3 sickle mower 1944 B, 2 1948 G's. Misc other equipment that my wife calls JUNK!