John deere 40

to30man · Mar 31, 2017

Have a 6volt John Deere 40 want to change to 12 volt what all has to be changed to use a one wire alternator thanks

CPeter · Mar 31, 2017

Only one question. Why? I have a 40 crawler and a 420U. The 40 was converted by the PO and the 420 is stock 6V. Both will start very nicely down to 0º. I would like to convert the 40 crawler back to 6V someday and just need to pick up a generator and voltage regulator.

Do you have trouble starting it? If so, why not fix the problem? 12V is hard on the nose piece of the starter and has been known to crack them with the extra "slam" when they engage.

Just my 2 cents worth. BTW, I have been running these things since 1971 and they are used to plow snow in New Hampshire winters and not "show queens"
CPeter

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to30man · Mar 31, 2017

Nice pic. The 40 belongs to my brother and
he wanted me to change it over because the
generator is locked up and a guy told him to
change I suggested just fix the generator. I
will pass your comment on and maybe he will
do that. It would probably be better for him
and me

Brendon-KS · Mar 31, 2017

I would second the opinion that a 6V system in good condition is all these tractors need. My Deere M (which is virtually identical to the 40, just a bit older) is 6V and always starts on the first or second revolution, even in sub-freezing weather and after long periods of unuse. I'd sure recommend fixing the generator and keeping the tractor original.

Rusty wheel · Mar 31, 2017

I converted my 40-w and I'm very glad I did. It starts quicker with no choke. U will have to change the light bulbs and install a volt meter in place of the amp meter. I got a volt meter from TSC with a light in it. I also installed an ignition switch with a key . I wired it so the light in the volt meter comes on with the key so if I look at the tractor and see the light on I know the key is on. U can leave the starter alone. Twelve volts won't hurt the starter as long as U don't crank on it too long. When U start the tractor, U rev up the engine to excite the alternator and it will start charging.

James Howell · Mar 31, 2017

"<font color="#6699ff">[b:654c4848f0][i:654c4848f0]Have a 6volt John Deere 40 want to change to 12 volt[/i:654c4848f0][/b:654c4848f0]</font>"

Take a look at the photo below of the starting motor switch on "BW" our 54 Model 40T.

The "hot" wire from the starting motor switch is connected to the ammeter.

Take a look at the photo below of the ammeter and ignition switch.

Note the "hot" wire from the starting motor switch to the ammeter shares the same post as the "hot" wire to the ignition switch.

The other post on the ammeter is connected to the BAT post on the alternator.

Take a look at the photos below of the alternator.

Either a warning light or diode should be installed in the wiring from the ignition switch to the 1 terminal on the alternator.

Take a look at the photo below of the warning light.

The photos above display the correct wiring for the alternator.

You need to determine the type of 12V coil is on your 40.

One type of 12V coil requires an external resistor.

Take a look at the photos below of the ballast resistor.

The photo below displays the coil.

Hope this helps.

John deere 40

to30man

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CPeter

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to30man

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Brendon-KS

Well-known Member

Rusty wheel

Well-known Member

James Howell

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