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John Deere Tractors Discussion Forum

John Deere B 8V to 12 Volt

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04-16-2018 09:49:32

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I know this questions has been asked, but I have not found the answer for this configuration and situation.

Early styled B. 6V positive ground. Cutout Relay. Magneto Ignition. Electric Start with a Freshly Rebuilt Starter.
This tractor was just purchased with a rebuilt engine. No Idea what size pistons were used, but it it has very good compression. Even with the petcocks open it will not crank freely with the 6V system.

What does it take to convert to 12V. Just replace the cutout with a 12V regulator? If so what would the wiring look like?

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04-17-2018 08:23:38

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 Re: John Deere B 8V to 12 Volt in reply to fixer2u, 04-16-2018 09:49:32  
Thanks John,

Looks like I gots some figurin to do.


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04-17-2018 06:11:07

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 Re: John Deere B 8V to 12 Volt in reply to fixer2u, 04-16-2018 09:49:32  
Thank you John T and old for the advise, Much appreciated!
John T, is there a specific voltage regulator you recommend for this application/configuration vs others?
Thank you!

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John T

04-17-2018 06:43:06

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 Re: John Deere B 8V to 12 Volt in reply to fixer2u, 04-17-2018 06:11:07  
Over the years and different models Deere used 3 terminal (BAT GEN FLD) and 4 terminal (BAT LOAD FLD GEN) VR's and I saw sooooooooo many get changed yet they were still for Class A (IHC and Deere used) and mostly 2 Brush gennys in later years.

If I were a betting man Id guess the 2 coil Voltage Regulators, the ones with a Cutout Relay and a single combination Voltage and Current Control Relay, might work better then a 3 coil VR, the ones with a cutout and separate Voltage and Current relays BUT ITS BEEN TOO LONG AND I FORGET WHAT I USED SUCCESSFULLY

Sorry, I just cant give you any specific make or model of VR to try and Id hate to see one get fried based on my recommendation. If I recall correctly (no warranty too long ago) I saw a few of the older 3 brush gennys and simple cutout relays using a manual Low High light switch charge control get changed from 6 to 12 volt use and all they did was adjust the cutout relay plus maybe the third brush location........ But that's NOT what you have it don't sound like.

A used true 12 volt genny and VR isn't all that expensive, but your idea may work okay (did for me) ITS YOUR CALL. Those 6 volt gennys likely had conservative field current ratings meaning a tad more of current then the max rating (more field current = more output) still wouldn't overheat them.

John T

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04-16-2018 10:08:46

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 Re: John Deere B 8V to 12 Volt in reply to fixer2u, 04-16-2018 09:49:32  
So when I converted my Farmall H to 12v with a distributor I did not need to get a 12v genny. I just added a 12v Regulator and a ballast resistor and used my original genny. I am getting over 13V from it.
Forgive me as my tractors are several hours away so I cannot look myself but are Farmall and JD generators that different?

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John T

04-17-2018 05:20:56

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 Re: John Deere B 8V to 12 Volt in reply to fixer2u, 04-16-2018 10:08:46  
I (when a used tractor dealer and farmer) converted several 6 volt gennys to charge a 12 volt battery simply by using a 12 volt Voltage Regulator and NEVER had any problems. The reason is a genny doesnt "necessarily" know what its output is to be, the faster it spins and/or the more current you pump through its field windings the greater its output (that's one function of the VR to regulate output by controlling fiedd current) . YES its still designed for 6 or 12 volt use WELL DUH but the above theory still holds true.

NOTES before anyone has a calf now:

I'm NOT saying that's engineering correct or the proper way to do it. I'm ONLY saying it works and I NEVER had any trouble.

It also might depend on what Voltage Regulator is used such as those having both Current and Voltage Regulation control relays versus those that use a Combination Voltage and Current control relay.

There could be a chance when this is done if the field coils draw too much current they may overheat but I NEVER had any problems.

I'm NOT saying this will work on ALL Gennys and ALL Voltage Regulators. Theres a huge difference in 2 brush versus 3 brush gennys and voltage regulators (2 or 3 coil etc). The ones I used and worked were Class A 2 Brush units.

THE CORRECT AND ENGINEERING PROPER METHOD is to have a shop convert the genny or just use a 12 volt genny and VR

You ask: "but are Farmall and JD generators that different?"

They are alike in that both are Class A so the above still applies

Hope this helps, I advise a non electrical person to do it the correct and proper engineering method so you dont risk damage to the VR or Genny.

Hope this helps

John T

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04-16-2018 11:26:38

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 Re: John Deere B 8V to 12 Volt in reply to fixer2u, 04-16-2018 10:08:46  
Most generator will not hold up well to trying to make them put out 12 plus volts there simply not wound correctly to do that for a long time

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04-16-2018 09:58:10

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 Re: John Deere B 8V to 12 Volt in reply to fixer2u, 04-16-2018 09:49:32  
To convert to 12 volts you need to add either a 12 volt generator or an alternator. If using an alternator you should change it to - ground since 99% of them are - ground. Many people use the 1 wire Delco but me I ALWAYS use the 3 wire like what is on a 1980 Chevy pickup

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