MT wiring

[Wing Nut]

It's me again! The MT I've acquired has been converted by a previous owner to 12 volts, and it apparently wasn't a very good conversion. Before I begin the restoration, I need to decide if I want to go back to the original 6 volt system or do the 12 volt conversion properly. I've found some 6 volt wiring diagrams online but I haven't been able to locate a wiring diagram for a proper 12 volt conversion. Does anybodyknow if such a diagram exists, and if so where would I get a copy? I'd also be interested in any opinions on 6v vs. 12v on this model, as it's my first John Deere.

Thanks in advance.
 

[leon]

I have no problem at all with the original 6 V. system on my MT. That's good for my personal preference is to leav'em original, but that's a personal preference thing.
 

[Ed the wine farmer]

My 1948 M is still 6 volts and it starts and runs just fine. I did rebuild the gen. and cleaned up the starter. I replaced the brushes in both. Hers a big tip -- clean all grounds. They are a great little tractor. My M came to the farm in 1955; to replace the horses. It"s still here and still working. Ed
 

[Mark-Ia]

www.jd40.com has a wiring harness diagram, it should be the same.
 

[James Howell]

All three of our 51MTs are original 6 volt systems.

Our 51M also has the original 6 volt system.

The 6 volt batteries turn the starters over with no problem and all tractors start very easy.

Had the generators checked on all four tractors.

Replaced the wiring on all the MTs.

Replaced the gauges and cutout relays on two tractors.
 

[Hotflashjr]

My MT has the original 6 volt system. Had to rebuild the on/off switch and solder on a new resistor but other than that no issues. It starts the tractor just fine. The other morning it was -3 and it spun it over without an issue. Make sure you get 6 volt light bulbs for your lights. Sharp's tractor has the reflectors with new chrome cheap. I'm not sure how long they will last but it made my lights 100% brighter.
 

[Rusty wheel]

I think the only advantage to converting to 12 volts is getting a battery. Six volt batteries are not as plentiful as twelve volts are.
 

[M-MAN]

If you are doing a true restoration it should have a six volt system but a genny, cut out, and a battery are going to set you back several hundred dollars. If you are actually going to use it keep the 12v. It's just my opinion but I woulden't give a plug nickel for any six volt worker. I've pushed, pulled and rolled too many of them back when I was young enough to do it.

You didn't say whether you have an alt or a genny? Also what is wrong that makes you think it isn't a good conversion?

If you do a search on johnnypopper I have the original 6v diagram on there as well as the 12v three wire Delco conversion I did on my M. I converted it about 30 years ago. There are several way's to do it and it's pretty simple. You take the original field wire and remove it from the switch forward. Then put a larger wire in place of the gen one and go to the alt with it. You can feed the alt plug from the big post on the back & use a diode to the No1 term or run it through an oil pressure switch like I did mine.
 

[Wheat Farmer]

I have had my 51 MT for 30 years. Still has the 6V, and I'm into my 10th year on the second battery. It had not been started for two years and I started it up a month ago without jumping it. I have two other tractors with 6V. My parts store needs 6V battery's on hand. Three different sizes. Smallest is $48.
 

[MEANJDK]

I considered changing my 51 MT to 12 volts for years, as it didnt ever start the best. I changed to electronic ignition, 6V, POS ground. Its the best thing I have done for that tractor now. It starts everytime, all the time.
Just saying...
 

[Wing Nut]

M-Man -

Sorry about the delay in my reply, it's been a crazy week. In answer to your question I'm not completely sure what I have. I've always been under the impression that all 12 volt systems had an automotive-style alternator. The battery is 12 volts but it appears I have a generator. I've included a picture. The tag shows that it's a Delco Remy and the only numbers that can clearly be made out are 1857, thanks to a back yard paint job by a previous owner.I've also noticed the ignition / light switch is bypassed and not being used.