Converting a JD 40S to a 12 volt system

[Jim in NC]

Does anyone have a diagram that would be helpful or perhaps something from James Howell that could be helpful to convert my tractor to a 12 volt system. I am using a Delco 3 wire alternator. That is what I have on hand. Thanks in advance for any help.

 

[M-MAN]

I haven't seen any posts from James since the change.

Here's one from a friend who used to be on johnnypopper.com. Hope it helps.

 

[JD39B]

Does anyone have a diagram that would be helpful or perhaps something from James Howell that could be helpful to convert my tractor to a 12 volt system. I am using a Delco 3 wire alternator. That is what I have on hand. Thanks in advance for any help.

Why convert it? Our 40S spins over fast and charges fine on 6v. 12v conversions in my experience are just a fix for a bigger issue.

 

[Jim.ME]

Why convert it? Our 40S spins over fast and charges fine on 6v. 12v conversions in my experience are just a fix for a bigger issue.

I am not saying a functioning 6-volt system won't work, but it seemed like keeping them working was getting more difficult. My 6-volt tractors aren't trailer queens, they work all day long when needed alongside the newer tractors, and I prefer 12-volt systems.

I can't speak for Jim in NC reasons for wanting to convert, but here are some reasons I have converted my 6-volt units to 12-volts:

Getting a good 6-volt battery that would last was hard and often the cost of them was more than the cost of a 12 volt battery that works.

Better lighting options for night work.

Able to boost other units if needed.

Can take the 12-volt air compressor and air up a tire on an implement when needed and move the implement in one trip. I have taps on all the tractors to run other 12-volt item if needed.

One 10SI/12SI 3wire alternator can cover several units. And finding an alternator that holds up is easier than finding generator regulators that last these days, at least for me.

To me it is each to his own, your tractor, make your way, I shouldn't question someone wanting theirs different. If I can help them with their project I will.

 

[Jim in NC]

Thanks for the help M-Man. Jim.ME could not have stated my reasons for changing the tractor any better. To add to the story this tractor was my Grandaddy's, my mom's dad. I was with him when he bought it in the mid 1950s. It is not the easiest tractor to get in and out of the seat, and that seems harder as I age. Yes it is a special tractor. At the same time it is a tool, and a tool that is easier for me to use and more efficient at the same time is a good thing.

 

[Jim.ME]

Thanks for the help M-Man. Jim.ME could not have stated my reasons for changing the tractor any better. To add to the story this tractor was my Grandaddy's, my mom's dad. I was with him when he bought it in the mid 1950s. It is not the easiest tractor to get in and out of the seat, and that seems harder as I age. Yes it is a special tractor. At the same time it is a tool, and a tool that is easier for me to use and more efficient at the same time is a good thing.

Does your 420 have an electric hour meter on it? I had a 430 crawler that had an electric hour meter with an oil pressure switch to control it. If by chance your 420 does, you can use the oil pressure switch to excite the alternator (you said you planned on using a 3 wire and the drawing M-man gave you only has the one wire). As you know, you will need some method of exciting it and preventing feedback to the ignition (diode, resistor, indicator light, oil pressure or other type switch).

 

[Jim in NC]

It is a 40 and has the switch and hour meter. I have it wired but I would like to use both the switch and meter. I have an idea as to how to incorporate the switch and meter into the system, but would greatly appreciate your input.

 

[Jim.ME]

It is a 40 and has the switch and hour meter. I have it wired but I would like to use both the switch and meter. I have an idea as to how to incorporate the switch and meter into the system, but would greatly appreciate your input.

You should be able to run a wire from the normal open terminal of the switch (same terminal that should be going to the hour meter) to the #1 spade terminal of your 3-wire alternator. The alternator won't back feed the meter if the engine is stopped (switch opens when oil pressure is gone). Make a short jumper to go from the #2 spade terminal to the alternator's battery output terminal to provide voltage for regulator sensing.

You will need to check your hour meter to see if it will accept 12 volts and to see if the terminals on it are marked for polarity as you will be switching to negative ground.

 

[Jim in NC]

Thanks. The hour meter does not work, and has not since I have had the tractor. If the switch does work it would hopefully excite the alternator. I have enough of the job done that the tractor starts , runs , and shuts off like it should. The charging a bit intermittent, and got it temporarily together shortly before dark today.

 

[buickanddeere]

Does anyone have a diagram that would be helpful or perhaps something from James Howell that could be helpful to convert my tractor to a 12 volt system. I am using a Delco 3 wire alternator. That is what I have on hand. Thanks in advance for any help.

Why ?

 

[M-MAN]

It is a 40 and has the switch and hour meter. I have it wired but I would like to use both the switch and meter. I have an idea as to how to incorporate the switch and meter into the system, but would greatly appreciate your input.

I have a gm oil pressure switch just below the alternator. Wire from the alternator output stud to oil pressure switch. Wire from the switch to the excite terminal. Switch is hot all the time but voltage is passed only when the pressure is there.

All you need for the hour meter is a wire from it to the switch. Just use a larger terminal and crimp it together with the wire going to the excite terminal.

 

[J.Wondergem]

Why ?

Why not?