3020 24 volt

So I got my injector pump off and it is getting rebuilt. So while im waiting for it to get back I figured I would nose around and look under my cab and I find 2 batteries on both sides of the tractor, with the left side being hooked up positive ground and the left side hooked up negative ground. after reading through the old threads here I noticed this is a hot topic. Whats all the fuss about in a nutshell?

I don't think there's any real fuss among all of those persons truly knowledgeable and electrical engineers and electrical techs and John Deere mechanics about the system, the John Deere Service Bulletin 268,,,,,,,,,,,, and allllllllll John Deere Wiring Diagrams,,,,,,,,,,,,, and alllllllllll John Deere Tractors,,,,,,,,,, show/have the 2 wire 24 volt devices (Starter, Generator) as FLOATING and insulated and electrically isolated from frame chassis ground and certainly NOT POSITIVE GROUND as has been erroneously posted here (perhaps that's the fuss you're thinking of???).

The center series tie point of the batteries (+ of one, - of other) does have an attachment to frame ground, that way there's two 12 volt (with respect to frame chassis ground) A & B circuits up to the switch as the diagrams show. In addition to the 2 wire FLOATING NON GROUNDED 24 VOLT SYSTEM there are 12 volt devices like lights etc.

Piece of cake, and no fuss as far as myself and other electrical engineers and techs and John Deere mechanics are concerned.

You new here? I dont recall you before and I been here over 15 years, but I dont remember every poster lol. Regardless Welcome, best wishes and God Bless

John T Retired Electrical Engineer

ya, im new here, only my 3rd or 4th post. my tractor doesn't have any lights on the fenders. they were removed for the cab that the previous owner put on. Why would one positive terminal be grounded to the tractor frame on one battery and one negative terminal on the other battery be grounded? am I understanding right when the batteries aren't actually two connected to make one, but two separate batteries that have no connection to each other what so ever

(quoted from post at 17:16:32 08/16/14) am I understanding right when the batteries aren't actually two connected to make one, but two separate batteries that have no connection to each other what so ever

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You need to do a little research on attaching batteries in series which
increases the voltage. Hooking 2 twelve volt batteries in series such as your 3020 gives the system 24 VOLTS.

Tx jim I see you here a lot. You should charge people for your knowledge. So if I had to charge the batteries you would have to charge them one at a time right? I never owned a tractor that had a 24volt system. I think im giving this to much thought like when I had to remove my injector pump

You could charge both batteries at the same time attached to tractor only with a 24 volt battery charger. With a 12 volt charger you can charge each battery one at a time still attached to tractor by attaching + to+ & - to - on each battery INDIVIDUALLY. You can also jump off a 24 volt system using 2 twelve volt sources by attaching each the same(+ to + & - to -) making sure no bumpers touch tractor metal surfaces. BTDT many times.

3020 guy, you ask:

1) "Why would one positive terminal be grounded to the tractor frame on one battery and one negative terminal on the other battery be grounded?"


First of all, if you put two twelve volt batteries together in series (+ of one ties to - of other) you end up with 24 volts. That powers/operates the 2 wire 24 volt Starter and 24 volt generator which charges the series battery connection i.e. both batteries are charged at once since current flows through both (they are in series remember). HOWEVER that 24 volt system has no electrical connection to frame ground, its floating and NOT POSITIVE GROUND as one person posted here.

NEXT at that center tie point where the two batteries are joined together in series there is a connection to frame ground. That's why you see the + of one and - of the other tied to frame ground. That's serves as BOTH a frame ground connection (for 12 volts NOT 24) and it ties the batteries together in series. Understand????? Okay since one 12 volt battery has a - terminal to frame ground and the other 12 volt battery has a + to frame ground THERE EXISTS 12 VOLTS from the untied end of each battery to frame ground, its just that one is POS to ground the other is NEG to ground. The tractor has 12 volt items etc so you need 12 (NOT 24) to operate them and that's where the two A & B 12 volt feeds come in
which are wired up to the switch. Some of the 12 volt lights are to a battery that has its + to frame ground while the others are to the other battery that has its - to frame ground in an attempt to balance the loads and the two batteries
i.e. the reason for the A & B 12 volt feeds up to the switch. Each is 12 volts with respect to frame ground.


2) "am I understanding right when the batteries aren't actually two connected to make one, but two separate batteries that have no connection to each other what so ever"

NOOOOOOOOOOO the 2 are tied together in series. The frame is a conductor so if - of one and + of the other are tied to frame ground THE TWO BATTERIES ARE JOINED IN SEREIS TO MAKE 24 VOLTS.

NOTE I highly recommend you read John Deere Service Bulletin 268 dated August 1958 (I believe). I recommend it because it was written by the John Deere Engineering Department NOT by some non engineer person or some person not very technically proficient. Their publication agrees with how all the tractors were built and how all the wiring diagrams indicate. DONT TAKE MY WORD FOR IT EVEN THOUGH IM AN ELECTRICAL ENGINEER, IM SAYING TAKE JOHN DEERES WORD FOR IT INSTEAD OF SOME LAY PERSON.

See theres no real fuss here yayyyyyyyyyy

Final Note: I have attended Buick n Deeres excellent Seminar Workshop on the John Deere 24 volt system and he's an engineering type person so se what he has to say also.

John T retired Electrical Engineer

I have been dealing with these Electrical nite mares for years,, and I have successfully converted hundreds of them over to modern 12 volts, and made life better for all concerned,, you guys can talk theory and operation of the 24 volt system all day,, what you can not explain is how a little bit of corrosion in a switch or voltage regulator can can cause the whole system to fail starting with Ghostly power drains,and 12 volt lights getting fed 24 volts blowing them like flash cubes, and there is the issues of trying to keep a bale or planter monitor working or trying to find a reverse polarity radio...put the 24 volt stuff in the trash can and go on...

3020guy, you've heard it from the MASTER!

I'll 2nd what Tim stated. Changing a 24 volt system over to a 12 volt system is easy and the only really logical thing to do.

I have an early 4010 and a 67 3020 that have the two batteries in them. I think of them as 2 twelve volt systems, one pos ground and one neg ground. The terminals need to be kept clean and both batteries need to be good. They work fine, Updating to a twelve volt system may simplify every thing but not necessary.

(quoted from post at 08:07:32 08/17/14) Updating to a twelve volt system may simplify every thing but not necessary.

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I suppose you've never seen a 24 volt JD tractor that's had an electrical created fire that started under the dash??

Wow I think we made it through two weeks without the infamous 24V topic coming up

Mornin Tim, what "guys" you talking about??

"you guys can talk theory and operation of the 24 volt system all day,, what you can not explain is how a little bit of corrosion in a switch or voltage regulator can can cause the whole system to fail"

Who cant explain it?? I CAN !!! (and I bet Bob and Buick n Deere and Tx Jim can also)
Corrosion develops into a resistive current path which causes voltage drop. If one current path develops a high resistance due to corrosion, current can seek alternative paths which may include backfeeding a device. The trouble is that hybrid dual 12 24 volt system has so many current paths and so many places where corrosion can develop ITS A NIGHTMARE LOL

It was NOT John Deeres best moment and Im NOT a fan of it but still try to help people best I can.

There ya go, fun chatin with ya, best wishes n God Bless

John T

(The trouble is that hybrid dual 12 24 volt system has so many current paths and so many places where corrosion can develop ITS A NIGHTMARE LOL) That"s the part I was getting at John, and my thought is unless some one is dead set on restoring one let the Nightmare stop...I don"t waste brain space on 24 volt systems anymore :^)

Hey I got no problem if someone wants to convert to 12 ITS SOOOOOOOO MUCH SIMPLER. One problem is its a rats nest behind the dash plus any old color coded wire is long faded and couple that with the 12/24 system WILL DRIVE A PERSON TO DRINK. Plus it don't even matter if you do understand the theory, its still so hard to trace and troubleshoot and NOT something the average Joe can do. As I said somewhere else it was NOT Deeres shining moment lol

John T

Yep and theres reasons for so many 24 volt questions. 1) Its so freakin complicated and 2) theres always new people coming on board. However we still do our best to help...

John T