Home Forums Miscellaneous Topics Rural Living Early model John deere 4020 24 volt system

I have an early model 4020 with the 24 volt system. I am familiar with the way the system is split into two 12 volt systems, one negative ground and one positive ground. I considered converting it to 12 volt but my alternator and starter both work just fine, both of which are 24 volt.

The reason to convert would be to put lights on it. LED lights are brighter and use less power. Most LED lights are rated for 12-24volts. Any reason not to leave it 24 volts, use LED lights and make the whole system 24 volt negative ground? Seems like it would be simple and not very expensive. Two 12 volt batteries are better than one for the increased cranking amps even in a 12 volt system. What am I missing here?

I think you need to study up on the negative ground or not. and study up on parallel and series hookup of batteries..

Queso here’s the deal. John Deere came out with the 4020 tractor in 1963. The early model diesel tractors had an isolated 24 volt system with two 12 volt batteries wired parallel, a 24 volt starter and a 24 volt generator. The system was not grounded to the frame of the tractor. The accessories (lights and gauges) were 12 volt split system. One side of the tractor was negative ground and the other side was positive ground. Without going into a lot of detail, the system was balanced through the light switch so there was equal draw on both batteries. Not one of John Deere’s better ideas. I think they borrowed Ford engineers to come up with this system.

Later in production they came out with cabs, heaters and air conditioners. The later tractors had 12 volt systems with batteries wired in series. John Deere sold conversion kits to convert the old 24 volt tractors to 12 volt. True to form, the kits were expensive coming from John Deere. I think the kit was like $500 back in the day and $1,500 or up now. There are conversion kits starting about $400 but like most things you get what you pay for. The starters are the weak point in the less expensive kits.

My tractor is still 24 volts. The starter and and alternator are in good condition. Modern LED lights will work over a larger range of voltage than the old incandescent and halogen lights. The old 12 volt lights are very bright when 24 volts are applied but they don’t last long. Also 24 volt gauges are easily available and some don’t care about voltage. The original fuel gauge and generator light worked on 24 volts.

My original question has to do with replacing the lights with 24 volt LED lights and keeping the 24 volt alternator and starter. The more I think about it, I am thinking grounding to the frame may or may not be a problem. Worst case I would have to run a ground wire and hot wire to each light with the system remaining isolated from the frame. I was just asking if anyone else had any ideas on why it might not work. I can explain it to you but …

The 12 volt systems seem to start pretty good
My late model 4020 has 2 6 volt
And starts real good
A trick for those is to turn up the pump
Gives a bigger shot of fuel and they crack right off

Yes. In the late 60’s they improved the 12 volt system and it does work good. The conversion from 24 volt to 12 volt also works well if you spend the money to get good components. The less expensive components are hit and miss. I did not mean to imply otherwise.

Don't know crap about JD or 4020s. Know a little bit about electricity though. Unless I'm gravely mistaken, you're mixing up your parallel and series definitions.

Two 12V batteries in parallel would give you double the amount of 12V current you could provide, either in power, or total energy delivered.

Two 12V batteries in series, would give you 24V between the negative terminal of battery A, and the positive terminal of battery B. If that's the case, as you said, why not just wire up your LED lights separate from the rest of the electrical system? Depending on the draw of the LED lights, you may or may not want to use a relay.

I think I would run 2 wires, one from the neg and one from the pos of 1 battery, thru a switch and to the LED lights. Looking at the wiring schematics this tractor has 1 neg ground and 1 pos ground. Strange to say the least. Dont ground the lights to the frame.

That is exactly what I’m thinking. 24 volt starter has a hot wire from the solenoid and separate ground wire terminal. Does not ground through the starter frame. Positive ground system. Like I said, I think John Deere borrowed Ford engineers to design this morphodite system. Checked continuity to the frame and starter/charging system is independent of the frame.

If you go with LED lights, they don't use nearly as much power as incandescent lights. Besides, you most likely will have the tractor running when using the lights, so that is a mute point anyway.

No need to re-invent the wheel.....

Great minds think alike. Plus LED’s operate over a range of voltage. If/when my starter and/or alternator go out and I convert to 12 volt the lights will still work.