4020 24v starting system wiring question

[Mcrafty1]

I have a new to me JD 4020 with the 24volt starting system, using two 12 volt batteries, I don't believe it's wired correctly. Here's how the wiring is routed now:

Beginning at the starter, a wire from the solenoid on the starter to the negative post on the LH battery, a wire from the positive post of the LH battery crosses over the transmission to the negative post of the RH battery, a wire from the positive post of the RH battery goes back across the transmission to the field post on the side of the starter. To my thinking, the wires are crossed at the starter? unless the system is positive ground? is that the case? Can anyone help me with this? Thanks

 

[Tramway Guy]

Here is a pretty good description of the ‘split load’ 24V system:

The John Deere 24 Volt Electrical System Explained

John Deere 24 Volt Electrical Systems on Electric Start 70, 720, 730, 820 and 830 Diesels

petcaretips.net

 

[JD Dave]

The hookup you describe is probably correct and will provide 24 volts to the starter. The starter doesn't care about polarity and will work okay either way. That being said, some parts of the system are polarity-sensitive which are the charging system and the fuel gauge. The system isolates the 24 volts from the frame of the tractor and 12 volts are picked off to run the lighting system via designed methods. You should get ahold of a service manual for the the serial number range for your tractor and make sure someone hasn't installed the batterys backwards. Your friend is John Deere Publications where you can find reprints of every manual they ever published.

 

[Mcrafty1]

Here is a pretty good description of the ‘split load’ 24V system:

The John Deere 24 Volt Electrical System Explained

John Deere 24 Volt Electrical Systems on Electric Start 70, 720, 730, 820 and 830 Diesels

petcaretips.net

That's a pretty in depth explanation ...However I'm old and slow...and thickheaded so not much could I grasp. That being said the picture titled Battery Hookup was similar to what I have other than the wire that routed through the switch may be the wire coming from battery B to the post on the side of the starter ( not sure about that though i can only see either end) rather than the wire from battery A to the solenoid. Thank you for that info too.

 

[wore out]

Your description of the batteries-starter wiring is CORRECT and EXACTLY how the tractor left the factory!

 

[Tx Jim]

On JD 24 volt electrical system starter, generator & voltage regulator have ""no ground"" because those items are insulated from tractor frame. There should be a smaller ground wire on LH rear battery post to tractor frame that provides a ground both + & - for electrical 12 volt accessories

 

[Mcrafty1]

The hookup you describe is probably correct and will provide 24 volts to the starter. The starter doesn't care about polarity and will work okay either way. That being said, some parts of the system are polarity-sensitive which are the charging system and the fuel gauge. The system isolates the 24 volts from the frame of the tractor and 12 volts are picked off to run the lighting system via designed methods. You should get ahold of a service manual for the the serial number range for your tractor and make sure someone hasn't installed the batterys backwards. Your friend is John Deere Publications where you can find reprints of every manual they ever published.

Thank you, I will go there and get me a manual, I'm going to need one.

 

[Mcrafty1]

On JD 24 volt electrical system starter, generator & voltage regulator have ""no ground"" because those items are insulated from tractor frame. There should be a smaller ground wire on LH rear battery post to tractor frame that provides a ground both + & - for electrical 12 volt accessories

Thank you for that, I did see a wire in that battery box that wasn't hooked up I believe that will be the wire you mention, if I recall it was grounded to a bolt on the transmission and the other end was just a small forked wire connector...probably was jammed in between the post and the clamp at one time and didn't make it back or just came loose. I will check when I get back to the machine and be sure to connect it.

 

[Tx Jim]

You're welcome
Actually attaching an inline fuse holder with a 30 amp fuse is better than just a wire for an accessory ground connection

 

[Mcrafty1]

You're welcome
Actually attaching an inline fuse holder with a 30 amp fuse is better than just a wire for an accessory ground connection

Thanks again, to be clear you mean the left rear battery positive post correct?

 

[Tx Jim]

Thanks again, to be clear you mean the left rear battery positive post correct?

LH rear battery post for accessory ground wire connection is correct if batteries are installed correctly.

 

[buickanddeere]

As much as I am a purist for restoration etc . With a 24V system . The best plan is a 12V conversion and a 5Kw starter .

 

[Tx Jim]

As much as I am a purist for restoration etc . With a 24V system . The best plan is a 12V conversion and a 5Kw starter .

I agree 12 volt starters are much more powerful than 60 yrs ago. 12 volt system is much better/simpler than JD's 24 volt system.

 

[KJB1053]

Yes these tractors use the frame to achieve 24 volts ( 2 - 12 volt batteries connected in series ) to hard to explain here so get the book
However I think it is Steinert who sells a complete kit with instructions and wiring diagram to put it to a 12 volt neg ground system , comes with new starter and alternator which is the way to go ( my cousin did this ) unless u r restoring it

 

[Tx Jim]

Yes these tractors use the frame to achieve 24 volts ( 2 - 12 volt batteries connected in series ) to hard to explain here so get the book
However I think it is Steinert who sells a complete kit with instructions and wiring diagram to put it to a 12 volt neg ground system , comes with new starter and alternator which is the way to go ( my cousin did this ) unless u r restoring it

Sorry but you made an incorrect statement. On JD 24 volt electrical system the starter, generator & voltage regulator were insulated from tractor frame. Small ground wire attached from LH battery, positive post to tractor frame supplies 12 volts both + & - to operate accessories such as lights & fuel gauge

 

[Mcrafty1]

I will be converting to twelve volt system asap, for now I'm going to keep it as is and work the tractor some to access the overall condition and build from there. It's not going to be a restoration, I will be making the tractor reliable and using it as a working piece. Thanks all for the great information, the forum has already proven to be very useful. I did order a service manual from the link on this site and should have that in a few days. Thanks again to all for the help.

 

[Tx Jim]

You're welcome

 

[KJB1053]

Sorry mcrafty ;;Didn’t mean that to be incorrect , I just remember one battery is positive ground to the frame and the other is negative , that’s the short version of how the 24 volts is achieved.. , yes there is a lot more to it

 

[wore out]

Sorry mcrafty ;;Didn’t mean that to be incorrect , I just remember one battery is positive ground to the frame and the other is negative , that’s the short version of how the 24 volts is achieved.. , yes there is a lot more to it

"one battery is positive ground to the frame and the other is negative"

"that’s the short version of how the 24 volts is achieved"

Has NOTHING to do with "achieving 24 Volts", it's all about "achieving" the (+) ground and (-) ground 12 Volt lighting and instrument power sources allowing the use of a 12 Volt fuel gauge and common 12 Volt lamps on a 24 Volt system

 

[wore out]

I will be converting to twelve volt system asap, for now I'm going to keep it as is and work the tractor some to access the overall condition and build from there. It's not going to be a restoration, I will be making the tractor reliable and using it as a working piece. Thanks all for the great information, the forum has already proven to be very useful. I did order a service manual from the link on this site and should have that in a few days. Thanks again to all for the help.

Unless you have a "bad" generator or alternator or especially a "bad" $$$ starter there's no need to rush into a 12 Volt conversion.

The 24 Volt system worked when the machine was new and will work just fine today with a little maintenance (as everything needs).

If and when a major component such as the starter fails it DOES make more economic sense to convert to 12 Volt.

If the tractor is not used on a regular basis a battery disconnect switch is a nice thing to have.

https://imgur.com/oSinb9J

(I own a gas 4020 PS and a (still) 24 Volt diesel 4020 PS.)