3020D electrical question.

ghuds

Member
I?d like to replace the old broken cab lights on my
3020. The wires coming from the switch to the rear
of the tractor are reading 24v (positive ground). My
question is - can I install led lights that are rated for
24 volts? Also, I thought the lighting circuit on this
tractor was supposed to be 12v. Does this sound
right?
 
No, it does not sound right. But there is an often done wrong thing that might have you in this position. You might have your volt meter set for AC voltage instead of DC voltage and because of the way the meter is made, it is now reading twice the voltage it actually is getting. So operator error has you thinking it's 24v when it's actually 12. I see no reason you can't go with 12 volt LED lights.

So a back up test to do is to reverse your leads and note if the negative sign shows up which will only happen when you are on VDC and you have the leads backwards to their red and black colors. If it still says 24 volts or nothing then you have a first clue that the meter is not set right. Don't worry too much about it either, I do it all the time and I certainly do know better.
 
When it left the factory, it was set up to run roughly half the lights run on (+)12 Volts and the other half on (-)12 Volts.

Unless someone has deliberately mucked with the wiring, at the very least you are missing the wire, fusible link wire, or wire with fuseholder that connects the midpoint of the series-connected batteries to the chassis or it's blown. You didn't mention your serial number, actually, the earlier ones were set up a little differently, but many were updated for short/fire protection issues.

Another common area problems is confused connections at the starter and solenoid, and there's many other things that can go wrong.

To a person familiar with the (rather odd) 24 Volt system with the midpoint connected to the chassis, making for two 12 Volt sources it would take but a few minutes to figure out what's going on, upon getting "hands on" with it.

But tough to diagnose "remotely".

You either need to find such a person, or get a factory shop manual and study up on it and become your OWN DEERE 24 Volt "expert". IMHO!
 

Ditto what Bob stated headlamps are supposed to be 12 volt operated.

Another option would be to convert 24 volt system to 12 volt system & save yourself a lot of headaches. Seeing that your tractor has a cab converting to 12 volt electrical system would be a little complicated that normal 24 volt system especially if it has AC.
 
Call green magazine and ask for a reprint of three articles I wrote on the 24 volt system. They are april 2013, and march and april 2014.
 
Ghud, good questions, those dual hybrid 12/24 volt systems are hard to understand for some. Good info below from Jim and Bob, and I will answer your questions and provide more information. If you ever get a chance and Buick n Deere presents another 24 volt Seminar Workshop like the excellent one I had the pleasure to attend TAKE IT IN !!!!!!!!!!!! he as well as Tx Jim and Bob know their 24 Volt stuff???..


1) You posted ?I?d like to replace the old broken cab lights on my 3020. The wires coming from the switch to the rear of the tractor are reading 24v (positive ground).

FYI the source of 24 volts is the series connection of two 12 volt batteries. It?s used to power the two wire 24 volt FRAME ISOLATED starter motor while the series 24 volt battery configuration is charged by the also FRAME ISOLATED 24 volt generator system. UNLIKE a 12 volt tractor, those gennys and starters have no electrical connection to frame, they are TWO WIRE 24 VOLT ISOLATED UNITS

The 24 volts WAS NOT from the factory Positive ground, its FLOATING with respect to frame. The starter motor and genny system are ISOLATED OFF FRAME and the 24 volts is from the + of one battery and ? of the other as 12 + 12 = 24 WELL DUH.

At the series center tie point of the two 12 volt batteries (+ of one and ? of the other) there?s a jumper wire connected to frame ground, therefore, one battery has its POS connected to frame while the other has its NEG connected to frame DUH?. That?s how two 12 volt sources are derived, one 12 Volt battery is POS grounded while the other 12 Volt battery is NEG grounded BUT THE 24 VOLTS IS NOTTTTTTTTTTTTTTT GROUNDED?..

The lights are 12 volt, some are connected/switched via the A & B (Pos/Neg) fed light switch to the NEG grounded battery with others the POS grounded battery. Obviously if two identical 12 volt lights/loads are wired across the 24 volt series battery connection even without that center tie point frame connection each would still work but NOT if one was burned out and open just like those old series Christmas lights.

NOTE if you?re actually reading 24 volts positive ground it?s not wired correctly BECAUSE if correct you would read 12 volts NEG ground or 12 volts POS ground depending if your fed off the A or B circuit, one battery or the other.

NOTE HOWEVER If you?re measuring across the A & B light switch feeds (One Pos other Neg Grounded) orrrrrrrrr somehow across the series connection of the two 12 Volt batteries THAT WOULD INDEED BE 24 VOLTS

NOTE HOWEVER the 12 volt lights are ONLY 12 VOLTS and fed from one or the other 12 volt batteries, one or the other A or B light switch feeds, one or the other of the Pos grounded battery or the Neg grounded battery???...

BUTTTTTTTTTTTT if wired right there WOULD NOT be 24 volts to frame ground


2) My question is - can I install led lights that are rated for 24 volts?

Even if it would work that?s NOTTTTTTTTTTTTT how I would do it.



3) Also, I thought the lighting circuit on this tractor was supposed to be 12v. Does this sound right? YESSSSSSSSSSSSSSSSSSSSSSSSSSS

YES the two lighting circuits are 12 volt. The lights are fed off the A B light switch which has 12 volt feeds from the POS grounded battery as well as the NEG grounded battery.

NOTICE do NOT take my word for it.. This is NOT my design, BUT

IT IS how Official John Deere Service Bulletins indicate,
IT IS how official John Deere Wiring Diagrams indicate,
IT IS how they were wired from the factory,
and as a used tractor dealer, farmer and electrical engineer who used, worked on, and farmed with those tractors I can tell you THEY WORKED AS DEERE BUILT THEM

SOOOOOOOOOOOOOOO if how Deere built them,,,,,,,, And their wiring diagrams,,,,,,,,,,,And service bulletins indicate is wrong or can?t possibly work that way GO FLAME AND TELL THEM NOT MEEEEEEEEEEEEEE LOL

Hope this helps

John T Retired Electrical Engineer
 
Thanks for all the input. It?s a lot to take in. I?m no electrical expert, but I have some knowledge of 12v systems - this ones a bit challenging.
I?ll have to look at a wiring diagram and compare it to the tractor. As far as I can tell, the wiring under the console hasn?t been messed with,. The only thing I can see is the previous owner installed a keyed ignition switch. He ran a direct wire from the LH battery to the switch and the return wire to the starter solenoid.
Everything else works on the tractor with the exception of the fuel gauge (the sender is bad). The cab has heat and air but the tractor isn?t equipped for either. I don?t really need them. A working windshield wiper would be nice though.
There are 5 wires in a harness running along the LH axle, and 4 wires on the RH axle. The only ones I can get a voltage reading is the green one. Like I said, it?s 24v positive ground. My volt meter is digital and switches to DC automatically. If I reverse the leads it reads negative.
I really don?t want to convert it to 12v, I just need a couple of lights for moving snow at night.
 
Lets try and make this simple. Look at the left hand battery. There should be a small wire from the back post over to one of the transmission top cover bolts. IF this wire is gone or broken you will get 24 volts to the lights.
 
(quoted from post at 22:43:16 07/07/18) IF this wire is gone or broken you will get 24 volts to the lights.

Actually, you won't, unless there's either other wiring mucked up and/or some burned out lamps.

With all lamps and wiring functioning as they left the factory, the light loads are nearly balanced on each 12 Volt battery, and the 24 Volts will be pretty closely divided between the two batteries, even WITHOUT the centerpoint "ground" wire being intact.

The fuel gauge and the alternator warning light may not function correctly with the lights "OFF", though, with the little center ground connection missing.
 
Bob I have had several tractors over the years have all the lights burnt out from 24 volt on 12 volt bulbs. The only thing needed was to replace the middle ground. I am not an electrical engineer or wiring guru but have fixed these darn systems for a lot of years.
 
Well the tractor is 12 volt.
It's never 24 to ground either even during starting or charging. You are still reporting an impossible voltage by all I know to be correct and true - so I just can't believe you.

Lighting system is 12 volt negative ground and positive ground. You will be able to find 12 volt negative ground LED lights quite easy, you will not be able to find positive ground LED lights at all. What is the make and model number of your meter?

<a href="http://charliemckinley.com/3010/Gary_Wece_Wire_Diagram_colored.pdf" target="_blank">Wiring diagram</a> shows six wires on keyed ignition switch. You may need to purchase an actual replacement key switch for that tractor in order to have access to power for lighting system.
 

ghuds
You mentioned previous owner installed ign switch. This ign switch should have posts on it labeled batt A &amp; batt B to power each circuit for 12 volt headlamps. Electrical load for accessories on each battery must be equal or generator will not charge batteries correctly. I agree with JD Seller that I've seen headlamps turned black from receiving 24 volts
 
As far as the lights are concerned and in response to a few more posts below, here?s more information.

THERE IS 24 Volts across the A & B (One to the Pos grounded battery, other to the Neg grounded battery, and 12 + 12 = 24) light switch feeds AND THATS TRUE REGARDLESS if there is that center tie point to frame ground or not !!!!!!!!!!!!!!!!!!!!!!

Since one set of lights is fed from A and other B, ITS TRUE 24 VOLTS IS ACROSS "ALL" THE LIGHTS (with or without center frame tie point) HOWEVERRRRRRRRRRRRRR that 24 Volts would appear ACROSS TWO 12 VOLT BULB SETS IN SERIES SO EACH COULD STILL WORK AND NONE BURN OUT. IE there?s NOT 24 volts across a 12 volt bulb just because the center tie opens IF ALL IS WIRED CORRECT WITH NO SHORTS THAT IS.

THEREFORE I agree with Bob that it?s NOT "NECESARILY" true (but sure anything is possible subject to incorrect wiring or a short etc where you could get 24 volts on a 12 volt bulb burning them out!!!) if the center frame tie point were to break open THE BULBS INSTANTLY BURN OUT BECAUSE THEY ARE EXPOSED TO 24 VOLTS.............The 24 Volts (A & B, Pos & Neg ground, 12 + 12) is across TWO 12 VOLT BULB SETS IN SERIES, so each can (if all else is correct) see ? or 12 volts and still work............

NOTE 1 HOWEVER this only works correct (if center tie point broke open) if BOTH sets of lights or loads are equal having the same resistance so each receives 1/2 of the 24 volts IE 12

NOTE 2 HOWEVER WITHOUT THE CENTER TIE POINT RETRN if the two bulb sets were not the same resistance (maybe due to a short or other fault or incorrect wiring) one would burn brighter and/or burn out while the other be too dim !!!!!

NOTE 3 HOWEVER If there was no center tie point return and two sets of bulbs were in series IF ONE SET BURNED OUT NOOOOOOOOOOOO LIGHTS IN THAT 24 VOLT SERIES CIRCUIT WOULD WORK

NOTE 4 HOWEVER The fuel gauge is 12 volts and different resistance then the bulb sets so it wouldn?t work correctly in series with a 12 volt bulb if both were incorrectly wired in series across 24 volts.


THEREFORE now see why John Deere had that center tie point to ground !!!!!!!!!!!!!!!!!!!!!!!!!!!

a) With it in place, if one bulb set burned open (the A or B fed) the other circuit still works !!
b) With it in place, there?s 12 ?independent? (not relying on 24 volt series circuit) volts to the A & B feeds to properly power 12 volt bulbs wired across A or B feed and the center tie.
c) With it in place there can be 12 volts Pos or Neg grounded to a single 12 volt load such as say for example a fuel gauge if its wired from A or B to the center tie point

NOTE There can be hard wires instead of the iron frame used to return current to 12 volt bulbs but it still returns to the center tie point and that tie point and theory above is still in place? IE IT?S THE CENTER TIE POINT WHERE THE TWO 12 VOLT BATTERIES JOIN IN SERIES THAT COUNTS regardless if from there you use wires or the iron frame as a conductor.

AGAIN do NOT take my word for it and I know Bob and Tx Jim know all this, so remember

This is how John Deere (not mine) Wiring Diagrams show it
This is how John Deere (not mine) Service Bulletins show it
This is how John Deere shipped the tractors with one battery/set having its POS to frame/ground and the other battery/set having its NEG to frame/ground
THERES A 12 VOLT POSITIVE GROUNDED BATTERY AND A 12 VOLT NEGATIVE GROUNDED BATTERY and there?s 24 volts for starter and charging system across the series sum
This is how the tractors were wired from the factory AND THEY DID WORK

Best wishes and God Bless all here and all responders, fun and informative chat we have going

John T Retired Electrical Engineer in Indiana
 
'He ran a direct wire from the LH battery to the switch and the return wire to the starter solenoid."

It would help if you could show us his "mods" on this wiring diagram, especially "the return wire to the start solenoid".

R12751_________UN01JAN94.gif


Note the jumper wire or fused wire we have been referring to, Key#30.

Also, you never did give us a serial number, if under 068,000 it's a little different.
 
Yo Bob, his statement that you re posted"

"He ran a direct wire from the LH battery to the switch and the return wire to the starter solenoid. "

COULD BE A PROBLEM and could explain how he's getting 24 volts. The "switch" has BOTH the A & B Pos and Neg grounded 12 volt feeds and there's a battery cable/feed on the starter solenoid. So it depends on which switch feed wire he used and that scabbed connection could be his problem since as you already well know, its 24 volts across A & B ?????????????

Nice sparky chatting with you as always

John T
 
JohnT, also I've seen where guys replace the 24V "isolated coil" solenoid with a 12 Volt "grounded base" solenoid. One side of the coil in the correct "isolated base" solenoid coil is connected to the terminal labeled "R", which connects to the (+) 12 side of the system.

When you instead use the incorrect solenoid, the "R" terminal is internally connected to the (-) 12 Volt side when the solenoid engages. The smoke's gonna get let out somewhere!

The short-duration 24 Volts doesn't take out the solenoid coil, but the voltage out the "R" terminal and the path to chassis ground from the coils wreaks havoc with the (+)12 and (-) 12 volt accessory and lighting circuits.

Plus who knows how many other wires got swapped around over the years!
 

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