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Wayne, Journeyman
Category: Agriculture and Farm Equipment
Satisfied Customers: 9454
Experience:  34 + years as a mechanic
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Need A wiring diagram Deere 3020 with a Motorola

Customer Question

Need A wiring diagram for John Deere 3020 with a Motorola alternator

JD 3020 Serial number-132375R

Unit may have been poorly converted to alternator type system from a generator before we got it.

Submitted: 2 years ago.
Category: Agriculture and Farm Equipment
Customer: replied 2 years ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Provide Diagrams, Manuals, or Instructions. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 2 years ago.
Charge indicator lamp illuminates brightly with key on but glows dim after start up while running. Alternator was replaced and still has same symptoms. (Old alternator had arcing marks on the output stud area).
Expert:  Wayne replied 2 years ago.
Hi I'm Wayne
I will try ti help you with this
see if this helps you
Customer: replied 2 years ago.

This model 3020 has a diesel engine with the 24 volt cranking system, I believe it originally had a generator with two output terminals and has had a later model Motorola 12v alternator installed. It has several wires coming out of the wiring harness near the generator--- two of which are about 8 gauge and were connected to the alternator output. Two in a connector that plugs into a connector on the Motorola alternator's piggy back voltage regulator, two that apparently were either original field or armature connections, and an orange wire that is hanging in the bundle. It seems that the harness was set up from the factory for more than one generator / or alternator application.

I need to know the correct wire to terminal connections because the lights and dash instruments are 12v. I believe the original generator split polarity for the negative ground and positive ground battery (They are wired in series for the 24v starter)

I grew up on the farm and have been a professional automobile technician for 35 years.

I know just enough about this system to be dangerous.....can't just start poking wires to're gonna burn up something expensive.

Unfortunately I apparently forgot more about it than the local John Deere dealer knows. They act like they know nothing of this system (all young kids) and they say they would have to order a manual for this is a neighbor's tractor we are resurrecting for them to use after sitting idle a few years.


Expert:  Wayne replied 2 years ago.
Hi Sam
I have seen them have 24 volt of diesel,
12v for gas , I will see if I CAN FIND 24 V
Customer: replied 2 years ago.
This 3020 set up only used the 24V side of the system for cranking the engine, the alternator was 12v but charged both batteries if properly wired up.
Unfortunately it will also would blow the sealed beam work lamps on the fenders and fry instrument cluster if wired wrong because 24v would get to sealed beams....too many years ago to recall all the details without the wiring diagram ....but needs to be for Motorola Alternator set up.
Expert:  Wayne replied 2 years ago.
Yes I will try to find that for you
Customer: replied 2 years ago.


I'm still waiting on the wiring diagram for a John Deere 3020 diesel with the 24v cranking motor and the 12v charging system....the website keeps wanting $46.00 payment and a rating and I haven't got what I need yet.

John Deere 3020 Serial #123375R - Diesel engine (2 Batteries)

I need a wiring diagram for the charging/starting circuit.

This is my first time using this website and so far it hasn't helped me.

Nothing personal against you...this is an unusual problem I have but I need a diagram otherwise I would be better off buying a manual from John Deere for $90.00


Expert:  Wayne replied 2 years ago.
Hi ***** having a hard time finding 24 volt system
don't worry about the site, that is only a deposit
until you give a accept, you are never charged
Customer: replied 2 years ago.'s only 24v on the starter/cranking side of the system and 12v on the rest of the charging / lamps /instruments on dash.

I see why they got away from this set-up...pain to work on.


Expert:  Wayne replied 2 years ago.
Morning Sam
See if this helps