JD 3020 24 volt lighting problems

I have a John Deere 3020 which has a lighting problem. First it is blowing the fuse going to ground on the left battery on the positive terminal. SO it is getting 24 volts to the lights on the 2 outer lights. The 2 inner lights have no power. I thought something must be grounded causing it to blow the fuse so I found there was a ground from the positive side of left battery to ground, so I found it was coming from the starter on the positive post, so I took it to a repair shop where they told me the starter was ok. The only thing else I can think of is I had a mechanic change the fuel gauge as it was not working. He said he had to ground it to the opposite ground. I wonder if this could cause the problem? Do you have any ideas or what I should be checking to isolate this problem?
Thank You
Rick

A "mechanic" would have corrected the wiring problem based on the original schematic, NOT "ground it to the opposite ground"!

That being said, unless he did something REALLY stupid, it is likely that you have a short in the starting system or charging system from one side of the 24 Volt system to ground. In other words, in the battery cable, starter or generator/alternator-regulator area.

omnt400
Welcome to the BEST tractor site on the planet!!

It's amazing to me that lately these 24 volt questions just keep popping up by people that are either guests or new members. The only reason I state this is the fact that JD's 24 volt system has been hashed out,discussed numerous times and usually ends up very heated.

That being stated the most likely place for a grounded connection is frayed wiring harness or fields shorted in starter. My vote would be starter especially if the person that inspected it wasn't a qualified 24 volt starter repair person.

Welcome Rick, youre like the 4th "NEWCOMER" poster here who has asked 24 volt questions and the other three "gents" never got back with us or provided any feedback or were ever heard from again hmmmmmmm Who and where are those rascals lol Please let us know where youre from, how things turn out, any more questions, and again WELCOME.

Okay heres the deal. The innermost series tie point of the batteries (NOT the outer 24 volt + and - leads) is indeed connected to frame ground with that little jumper and there are TWO A & B voltage feeds up to the light switch, one 12 volt feed/battery is POS to frame Grounded, the other 12 volt feed/battery is NEG to frame Grounded, and those are for 12 volt loads like lights and gauges etc. NOW IF THAT JUMPER OR FUSE IS BLOWING OR BURNING its because ONE side (The A or B Feed) has a short or a too low resistance path to frame ground. Each A & B battery/feed is for 12 volt loads but if its lead is shorted to frame ground THATS A DEAD SHORT ACROSS ONE OF THE 12 VOLT BATTERIES therefore SHE BLOWSSSSSSSSSSSS

SO WHERES THE SHORT????? Okay, the 24 volt system/portion IS NOT POSITIVE GROUND as one person INCORRECTLY posted here, the 24 volt devices, starter and genny, are two wire devices that are electrically isolated from frame ground, they are FLOATING AND NOTTTTTTTTTTTTT POS OR NEG GROUNDED. Alllllllll other two cylinder Deeres 6 and 12 volt AREEEEEEEEE positive ground, the POS battery post is connected to frame ground BUT DONT CONNECT EITHER OF THE 24 VOLT LEADS TO FRAME GROUND they are for the 2 wire frame isolated devices ONLY.

Now, I used to be a used tractor dealer (also an Electrical Engineer) and also farmed with those old two cylinder 24 volt Deeres and did see shorts to frame ground develop in starters or gennys or in the mess of wires around that switch ITS A RATS NEST BEHIND THAT DASH. I know its not much help saying the shorts in the wiring harness or genny or starter BUT THATS THE BEST WE CAN DO NOT BEING THERE ARMED WITH A TESTER.

For one of the best articles that may help you understand, find or diagnose the problem, look back over on John Deere Forum a while back where a fine gentleman posted a link (and wil e mail it to you) to John Deere Service Bulletin (was it 268???) that explains the 24 volt system in detail. Or look on Duane Larson web site 2cylinderservice for that 24 volt system service Bulletin

Sorry we cnat help more, that system is hard to troubleshoot even if there armed with a tester let alone blind over the net GOTTA BE A SHORT

Again welcome, let us know more about yourself, give us some feedback, and give the JD Service Bulletin a look see BUT DONT POS OR NEG FRAME GROUND ANY OF THAT 24 VOLTS OUCHHHHHHHHHH

John T

When my dad bought his 3010D in 1970 it had one battery connected positive to frame and the other battery connected negative to frame. Was there ever a change made to wire them this way or is it something that a mechanic just thought was better? It has been that way for more than 40 years and does not seem to cause any other problems.

This was the tractor I on which i learned about the 24 volt system. I just picture it as one part of the lighting system is positive ground. The other half is separate from the first and is negative ground. The starting and charging systems are 24 volts and isolated from the tractor frame.

(quoted from post at 19:38:40 11/07/13) When my dad bought his 3010D in 1970 it had one battery connected positive to frame and the other battery connected negative to frame. Was there ever a change made to wire them this way or is it something that a mechanic just thought was better? It has been that way for more than 40 years and does not seem to cause any other problems.

This was the tractor I on which i learned about the 24 volt system. I just picture it as one part of the lighting system is positive ground. The other half is separate from the first and is negative ground. The starting and charging systems are 24 volts and isolated from the tractor frame.

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wen, that is the design of those 24v systems. No one changed anything.
Think two batteries in series (2 cell flashlight for example) with a center tap (where the two batteries connect together) grounded to chassis. Now a light from the unconnected end of either battery to ground (center point) will see 12v , although of opposite polarity (+/-). But if you need 24 volts for starter motor, just forget the center tap and connect from unconnected ends of both batteries (in series so they add). They charge them in series, too, with 24volts.

The change I think is that there is no fuse between a battery and the frame. I have battery cables that attach directly to the frame from each battery, one negative and the other positive.

That's how you get the 24 volts. The way you are describing the battery hookup is Series.

The question comes back to my tractor has the cables attached to the tractor chassis. My 4010 before I converted it to 12 volt had a cable running between the two batteries and another wire from one battery to the chassis with a fuse in it. I believe that was the original set up. Did John Deere make he change to eliminate the small wire with the fuse or was that a change that was not form Deere?

(quoted from post at 18:38:40 11/07/13) When my dad bought his 3010D in 1970 it had one battery connected positive to frame and the other battery connected negative to frame. Was there ever a change made to wire them this way.

Click to expand...

Owan
Ist New Generation 24 V systems came from factory as you describe.


3020's were changed to this style at SN 068000- and 4020's at SN 91000-

Thanks for the answer. I don't know what the serial number is but I do know it is a 1961 model year.

SN on 3010/4010 is immaterial as all 24 volt systems 3010/4010 came from factory as you described with a short woven wire cable at the rear of each battery.

John T.
Thanks for the reply to my message, I live in western Iowa. I meant to get back sooner but been busy working in fields. I appreciate you explaining how this works, with that I have a couple questions. Since I have a short, when I touch a meter positive on battery and go to ground or the frame, I get 24 volts on the left battery. I unhooked everything and found the starter was showing a ground from the positive battery terminal to the case. Is this normal or is it shorted there??
Also, I just had a mechanic replace the fuel gauge and he told me he had to change the ground from I believe he said positive to negative. Could this be what is shorting out the system?
I am getting confused but hope can figure this out. Thanks again.