John Deere B Conversion, 6 to 12 volt

What do I need to convert a 1947 (serial 201702) model B with a magneto from a 6 volt battery to a 12 volt battery? Can a resistor be placed inline so I don't have to change light bulbs? I want the 12 volt so it can start the tractor more easily. Would the 12 volt battery be negative ground? Thanks to all who respond.

I run mine 12 volt negative ground. I had the generator rebuilt for 12 volts and it has a 12 volt regulator. I did change the light bulbs to 12 volt. The rest is all original.

Thank you, Steve. Larry

Good question, here's my take"

1) Of course, being a Magneto, that part requires no changes.

2) The 12 volt battery could be POS or NEG grounded so long as:

A) Any new 12 Volt Generator (if a generator is used) is properly polarized and
B) The new Voltage Regulator (if such is used, if it uses a manual dash Low/High charge control system there's NO true VR
to deal with and different considerations) is suitable for the chosen ground. If you switched to an Alternator Id use
NEG ground

3) Sure a ballast of proper resistance and power could be used to drop voltage down to 6 for lights BUT I WOULD JUST CHANGE
THE BULBS

4) The old 6 Volt Starter can still be used, I've done it many times no problems even if this is NOT the ideal engineering
or correct answer.

5) If it has an existing working ammeter and iffffffffff polarity were reversed (original POS) leads need swapped

There are advantages and disadvantages for keeping a Generator or using an Alternator but you didn't ask so I'm NOT addressing that choice.

Similar some just use good quality 0 better yet 00 gauge battery and ground cables and a good heavy duty high CCA battery to improve cranking performance and NOT mess with 12 volt conversion. YOU DIDNT ASK SO IM NOT GOING FURTHER THERE

John T

Feel free to give your thoughts on keeping the six volt system. A new Napa commercial six volt was installed and it didn't do the job, so I suppose the starter could be checked, too. Any thoughts you have for installing an alternator as opposed to a 12 volt generator would be good to hear. I am not a purist but just want a tractor for participating in parades. Thanks, John.

No on resistor for lights, yes on everything else.

Its ONLY your choice to keep it 6 or go to 12. A Model B is not all that hard to crank n start as compared to an A etc. The starter motor can be bad and dragging Id recommend having it AS WELL AS THE STARTER SWITCH checked since a good battery and 0 Gauge Cables AND A GOOD STARTER AND SWITCH should crank a B okay. If the starter motor AND SWITCH are all good and you had 0 gauge battery and ground cables and a good battery but she don't crank as you like ONLY then Id consider going to 12 Volts and if so I'd use an Alternator and change it to NEG ground.

The ground cable needs attached to a clean shiny heavy frame member or direct to starter NOT any thin wimpy sheet metal or battery box, try that.

I have seen many many of those starter switches (or the copper starter post under the switch) go bad and they are cheap n easy to replace.

John T

Once you put a 12V alternator on a tractor you will wonder why you waited so long.

I have had my 46 B converted to 12 V for probably 20 years. 12V bulbs and 12V generator Positive ground. Works great!