Introduction: John Deere 3020 24v to 12v Conversion

About: I am by nature a geek and am not ashamed to say so. I decided to create this instructable account because I figured in my learning process I could also teach others. Feel free to look at my existing instructab…

I am going to start off this instructable with a story on why I am doing this instructable. While attempting another project and instructable on this tractor I ran into a bit of an issue (will be published later). The tractor would no longer start. I did a bunch of trouble shooting and found the culprits to be a battery cut off switch that was added and the starter solenoid. I was advised that I should convert the 24v system to a 12v system as it would be cheaperandeasier in the long run. This particular year of tractor was the last year that John Deere put the 24v system on a 3020 and apparently it can be pretty troublesome with battery drainage caused by the starter etc. I did not heed this suggestion and attempted to fix the issue and keep the tractor original with 24v.

So I ordered a new switch and solenoid, put it in and what do you know the tractor started great. Better than ever actually. Previously when the tractor died I noticed that the starter solenoid was VERY hot, to the point of melting its own plastic. So while the tractor was running I was constantly feeling the solenoid. Nothing was getting hot so I was good to go, or so I thought. I turn off the tractor and hear some popping and fizzing and get that familiar smell of electrical smoke. Ok maybe I have fried an electronic component or two in the past but I know that smell. I search all over the starter area and don't see anything smoking or burning. Then I see smoke rising from the other side, I run over and the generator is absolutely smoking. I immediately cut off the power at the switches and waited for the smoke to stop, the popping did but the smoke didn't. So I grab my fire extinguisher and shoot it directly into the generator. After a minute the smoking subsides.

Alright, time to get another voltage regulator and generator I thought. It's a new to me used tractor, I want to keep it original so lets see what they cost. Holy guacamole batman those things are expensive. I could change over the entire system for what they wanted for just the generator and have all new parts and not have to worry about it. So I began searching for the parts or a kit to switch it over.

Step 1: The 24v Theory of Operation.

Before we get into a bill of materials and the process I want to talk a minute about how the JD 24v system was supposed to work or at least what I understand of it.

In a way the system is 12v positive ground and negative ground with an isolated 24v starting/charging system.

Half of the accessories are 12v positive ground, the other half is 12v negative ground. It depends on which side of the tractor they are hooked up on. This basically separates the two halves into the two different batteries in order to balance the load on the different batteries.

The starting and charging portion of the tractor is 24v and is isolated from the accessories of the tractor. Apparently there has been a history of copper dust building up in the starter brushes and slowly draining and eventually killing one or both of the batteries. Quite a few people have put in a battery disconnect switch to help alleviate this issue, although it doesn't really solve the problem.


The cost of maintaining the 24v system is pretty hefty. The starter costs in excess of $500, the generator is in excess of $500, the regulator is somewhere around $150 and the batteries are $150 each, and that is minimum prices that I found for decent parts. At John Deere you are looking at around $2000 for the components. I can switch over the 24v system to a 12v system between $400 and $800 for all of the components, and if I wanted to eliminate one of the batteries I could. Then maintenance costs are cut way down, if my alternator goes out I can go down to the local car parts store and find a replacement for about $100. The same goes with the starter could find a local replacement between $250 and $330 depending upon the brand. .


Before we get into this I want to put out a few warnings here.

  1. Working with electricity is DANGEROUS to both you and your tractor, if you are not familiar with or even the slightest bit leery of your capabilities, STOP, find a professional. This instructable is meant to be a guide to those that are familiar with this kind of thing and I will not be liable for any damages to you, your helpers, your equipment or tools from improper knowledge or usage.
  2. Some other parts of your tractor may need to be rewired in order to work, I cannot predict extra accessories on your tractor and how they are wired. Make sure to check everything.
  3. Other components of your tractor will NO LONGER WORK AS DESIGNED. For example; the generator light. It will not work with this conversion. Instead it is recommended to install a voltage gauge in its place. Another example is your Fuel gauge will need to be replaced if you want it to work.

If you understand these warnings please continue. Now that we have that out of the way we can get to the conversion.

Step 3: Purchase the Materials for the 12v Conversion.

There are quite a few sources of a 12v conversion kit. They range in price from $330 to $900 plus shipping.

  1. In my research and talking with others that have worked on these for decades, the best kits are the ones that come with Nippondenso starters. They last the longest and are also the more expensive kits. The part number on this kit is A-TS-8000 and is available from multiple sources such as John Deere, A&I Products and a few others. Be careful though there are people that list the same part number that are selling a cheaper version of the kit that does not contain a Nippondenso starter. The cheapest price I found on this kit was at Tired Iron Tractor parts for $670, available HERE. I would contact them to ensure it has the Nippondenso starter if that is what you want. Note that this kit comes with the Starter, Alternator, Alternator bracket, wires, a solenoid but no voltage gauge.
  2. Rare Electrical has a kit available and is the cheapest kit at $340 and free shipping. In talking with them their kits are comprised with starters and alternators by Arrowhead electrical products. The kit consists of the Starter, Alternator, Alternator bracket, wires, a solenoid and a voltage gauge. This is available HERE. As a side note on this the part number on this matches the next manufacturer noted below but the rep said they don't purchase that kit they make the kit in house from available parts. This is the option I chose and after receiving the kit it was not what the person I spoke to had described based on my questions. It was a gear reduction starter vs direct drive and the nose cone of the starter was aluminum. I am continuing with this kit because I want to be a test subject and see just how long it lasts.
  3. Atlantic Quality Products make another kit, part number AKT0017. I called and talked with them and they state that the starter brand should be a Bosch. This kit comes with the same items as above and looks pretty much the same. There are a few sources for this exact kit as well but the best price I found on it was at Yesterdays Tractors, HERE. Note that this is one company listing the TS-8000 part number even though it is not, in speaking with the support rep it is the one from Atlantic Quality Products.

Those are just three kits that are available that I was looking into, whatever you do make sure to call the company and talk with them on the parts to check the brand of starter and make sure the starter nose cone is not aluminum. You want cast steel for the nose cone.

The other option is to source the parts locally but I had a hard time finding individual part numbers from the manufacturers to be able to do this.

As for me I chose option 2 because its cheaper and thought it might have been the same as option 3 and would come with a Bosch starter but it wasn't.Please remember that cheaper is not always cheaper, I chose the cheaper option due to budget constraints but it is not the best option. Basically my thinking is if it lasts me a year or two then I can upgrade to the better starter.

Step 4: Disconnect and Remove Your Batteries.

The John Deere 3020 24v system contains two batteries.

First you need to disconnect and remove both batteries.

  1. Start by disconnecting the cable from the NEGATIVE post on the left side of the tractor.
  2. Mark the battery cable you just removed as NEGATIVE with green tape or a label maker.
  3. Disconnect Positive Cable on left side of tractor
  4. Again Mark the cable with RED tape or a label maker
  5. Then Disconnect the Negative post on the RIGHT side of the tractor.
  6. Again mark the negative post you just removed as Negative with green tape or a label maker.
  7. Then disconnect the positive cable from right side of the tractor. Again making sure to label it with RED tape or a label maker.
  8. Remove the batteries.
  9. It is best to set the batteries on a piece of wood or rubber. This will prevent the possibility of the batteries draining while sitting.

I try to keep the batteries on the side they came off of so either label the batteries or remember where you set them.

Step 5: Remove the Hood for Ease of Work.

This step is optional, but it does help for working space We are going to remove the hood so that we can get to the existing voltage regulator easier.

First we need to remove the dash cowl by removing the 5 bolts and pulling it off then setting it to the side.

Now we need to remove the hood.

  1. Remove the air pre cleaner
  2. Remove the fuel tank cap. Be careful not to get any crud into the fuel tank.
  3. Remove the Radiator cap. Again try not to get anything into the radiator.
  4. Remove the rubber around the air intake pipe.
  5. Remove two bolts on rear of hood near cab with a 9/16" wrench.
  6. Pull out and up on the front mesh grate assemblies and set them out of the way.
  7. There is a hood latch on each side turn these outward to release the hood.
  8. With a helper lift the hood up over the top of the air cleaner pipe and the exhaust pipe. (Note in my video I removed the hood by myself, don't do this, its heavy and you could injure yourself)
  9. Set the hood off to the side.

Step 6: Remove Existing Generator and Bracket.

Now we need to remove the existing generator and bracket.

  1. Disconnect all of the wires from the Generator, there should be three wires
  2. There are three bolts on the generator. Remove the bottom two first then the top. Warning the Generator is pretty heavy, Have a hand on it when you take the last bolt out so it doesn't fall.
  3. When you remove the generator a shroud should also come off with it, set this off to the side.
  4. There are two bolts on the generator mounting bracket attached to the engine block. Remove both of these bolts and put them in a safe place. Set the generator bracket to the side, you wont need it again for this but if you ever want to change it back to a 24v system you want to keep it.

Step 7: Install the New Braket and Alternator.

The kit I purchased came with a new alternator bracket. The first thing we need to do is install this.

  1. Position the new alternator bracket with the alternator mounting portion to the front of the tractor and install the bolts loose to allow for adjustment.

You will need to temporarily install the alternator to check the alignment of the pulleys. The bottom of the alternator has a long hole or tunnel on it. This is the hole that needs to go onto the bracket. The bracket came with numerous washers. In my experience all of the washers needed to go to the back of the bracket between the alternator and the bracket. Basically just put the bolt through it and look at the alignment of the pulleys. If it does not align as mine did not you may have to use the old pulley off of the old generator. Removing pulleys is generally not a fun task and will require special tools in order to prevent damage to the pulley and/or the generator alternator. So you have two options, purchase the tools you need to make the swap, or you may be able to take it down to a local automotive repair shop and ask them to swap them for you. At this point I broke out my special tools, removed the pulley from the alternator and the generator and switched them. You do not want the pulleys to be out of alignment, if they are too far out of line it will cause premature failure of your belt. Once you verify alignment tighten the new alternator bracket before you install the alternator, the bolts will be hard to get to later.

Now that we have everything proper let's bolt up the new alternator.

  1. Again checking alignment and using the washers provided put the alternator on and slide the bottom bolt through. This time go ahead and put the nut on it, but don't tighten it.
  2. Rotate the Alternator up so that it is far enough in to get the belt on it. Note that you may have to push the tension bracket out of the way to rotate it up.
  3. Put the belt onto the pulley and make sure the belt is on all pulleys. Again check alignment.
  4. Install the bolt first through the tensioner bracket and into the threaded hole on the alternator. Dont tighten the bolt all the way.
  5. Go ahead and tighten the bottom bolt at this time.
  6. Using a pry bar, pry out on the alternator to create more tension on the belt.
  7. Once you are good with the tension go ahead and tighten that top bolt.
  8. Check the belt tension again, this process may take a few tries.

Your new alternator is now installed. We will come back to the wiring later.

Step 8: Remove the Old Starter and Solenoid and Install the New One.

We need to remove the old starter. Fair warning that the bolts on this starter are difficult to get to. The easiest way that I found to be able to reach everything is to first remove the solenoid from the starter. You don't have to do this if you think you can reach your hand or wrench back to the rear bolt of the starter.

  1. Remove all of the wires from the solenoid. There should be a yellow wire, two browns, two blues and your main power.
  2. Also remove the strap going from the starter to the bottom post of the solenoid.
  3. Remove the 4 bolts on the starter solenoid. I found that a swivel adapter or swivel socket works the best to get to the ones on the rear.
  4. Remove the solenoid and set it off to the side.

Now we can start to remove the starter.

  1. Remove the main negative line from the starter. At this point there should be no more wires attached to the starter.
  2. I found that I needed to remove the rear fuel filter to allow clearance for removal of the starter. WARNING Diesel fuel will spill out when you loosen this. Its best to find a way to prop the filter up in order to conserve the fuel in the filter.
  3. Remove the three bolts going to the starter.

Now we need to install the new starter. Installation is almost the same as removal but we are not going to take off the solenoid. Again the rear bolts will be difficult, take your time and try not to curse too much. The starter that came in my kit made access to the rear bolt a little easier with a socket wrench and an extension.

  1. Align the starter into the cavity it came from.
  2. Make sure the starter seats all the way in
  3. Install the three bolts into the starter
  4. TAA-DAAAAA its installed.

Again we will come back to the wiring in a few steps.

Step 9: Find a Place and Install the Secondary Solenoid.

I did a lot of what if thinking here. What if I have to pull the side cover, what if it gets hot, what if it gets wet etc. So I looked around a bit to find the best place in my opinion to install the starter solenoid. In my case I chose to put it on the panel under the steering wheel on the inside where the key switch is. Where you choose to put it is up to you, but you may have to drill a few holes so keep that in mind.

To install where I did:

  1. There is only one bolt holding that panel on. Remove it and set it to the side.
  2. Find the best place for install. Please see the images or video for my location.
  3. Set the solenoid on the panel and mark the mounting hole centers.
  4. Drill the holes out and using two bolts mount the solenoid.

Do not reinstall the panel as we now have to wire this thing up.

Step 10: Connect the Wires to the Secondary Solenoid and the Starter Wiring.

Now that we have the alternator connected we need to connect the wires to the secondary starter solenoid.

Since we installed the secondary solenoid a little further than the wires provided in the kit we made new wires to connect it.

Connecting the secondary solenoid.

  1. The yellow wire that originally went to the starter needs to go to this solenoid on the terminal marked "S". You may have to run a wire from the starter area back up to the solenoid to reach.
  2. Attach one of the red wires to the right side of the solenoid
    1. The other end of this wire needs to be attached to the top terminal of the new starter solenoid.
  3. Attach the other red wire to the left side of the secondary solenoid.
    1. The other end of this wire needs to go to the left small solenoid on the starter.

Now we will hook up the main battery cables to the starter. When we first started this I had you mark the cables on the battery end to note where they went. There should be two large battery cables coming from the battery boxes to the starter area. Previously one of these was negative and one was positive. Now they will both be Positive.

  1. Both of the battery cable wires near the starter should be connected to the top post of the starter.
  2. The brown and blue wires that are near the starter should also be connected to the top starter solenoid terminal. Please note you will probably need to put a new ring terminal to fit the terminal. OR you could make a jumper terminal wire like I did.

The starter and the secondary solenoid are now wired and ready to go.

See the wire schematic images of the previous 24v system

Vs the new 12v system

Step 11: Let's Hook Up the Alternator Wires.

I was originally going to put all the wiring in one step but I think that it is best that we break it down.

Lets go back over to the alternator side of the tractor. Right above the alternator is the voltage regulator. Connected to the voltage regulator is a wiring harness with three wires. While the colors can vary mine were brown, blue and black (could be pink).

  1. Remove these wires off of the regulator.
  2. You may need to add wire but we want to combine the blue and the brown wires onto a new terminal.
  3. Cut the old terminals off and combine all of them into one terminal if you need to add wire.
  4. You may be able to use the existing terminals and put them on the alternator as is.
  5. Attach the brown and blue wires to the battery terminal of the alternator.
  6. That is the only connection needed. The remaining wires can be capped or taped off and tied up.

See the before and after diagram of the voltage regulator - generator vs the alternator. You can choose to remove the regulator or leave it in but disconnected.

Please see the image of the 24v system with the generator and voltage regulator below.

vs. The new 12v system below.

Step 12: Installing the New Negative Battery Cables and the Batteries.

Now we need to install the negative battery cables. You have the choice of removing the old wire or just tying it out of the way. This wire would be the one that connected the two batteries together so you might need to pull off the floorboard to get this wire out.

  1. On each side find an existing bolt near the battery area that has a clean surface. If it's not clean, clean it. We need to make good contact here. I chose the bolt that holds the bracket holding the floorboard of the tractor. Again if it is not clean it is best to clean it, clear the paint from it, scuff it up a little bit and you should be good.
  2. Now install the right side battery, ensuring that you connect the wire going to the starter to the positive side of the battery. REMEMBER your left side positive battery cable now is connected with this one. Which means there is voltage on it. Ensure that it is not touching any metal.
  3. Install the left side battery again ensuring that you connect the wire going to the starter to the positive side of the battery.
  4. Ensure all of your switches are in the OFF position
  5. Now connect the new ground cables to each battery.

Step 13: Wiring Comparison.

Let's double check your connections. The first image is the entire wiring of the 24v system. The second image is the 12v system. Please ensure your wiring looks like the second picture.

Step 14: Lets Get Ready to Start Your Engines

At this point everything is hooked up now we need to see if this thing will start. Turn on your Key, press in the clutch (otherwise known as an inching pedal) and press the starter button. If everything is correct it should start right up.

Step 15: Thank You.

Thank you for watching, this instructable took several days of work on the tractor largely due to the alternator pulley and the weather, along with an entire day and a half of video editing, and another day to make the diagrams. I hope you enjoy it or at least somebody finds it useful.

Special thanks to the guys over at Yesterday's Tractors Forum for answering questions for me along the way. Keep watching for my next instructable on this tractor for moving the loader hydraulics off of the rear ports as well.

Thank you again!