4020 Diesel electrical system

*****************LONG ANSWER*********************

You have either (2) 12 volt batteries connected in series or (4) six volters which totals 24 volts, but the only things that run at 24 are the starter and charging system and they are both isolated from frame ground.

The batteries are connected in series with the + of one tied to the - of the other, and the center tie point of the batteries is also wired to the frame for frame ground. Then there remains 2 outermost untied battery posts, a + on one battery and a - on the other, which is 24 volts betwen those 2 outer posts. (Starter and charger 24 volt circuit)

Those 24 volt + and - posts are the ones connected to the starter and charging system. Some 12 volts to feed lights etc are fed off one outermost battery post to ground (thats only 12 volts, between one batterys outermost untied post and frame ground remember) and the other 12 volt loads are fed off the opposite batterys outermost untied post to ground.

Theres like two (A and B) battery circuits, each 12 volts between it and ground, fed to the switch. One of those batterys is positive grounded and the other negative grounded via that center tie point to ground as described above.

I hope this helps you and post back or e mail jmn50@msn.com or call (812) 824-4608 if you have any more questions.

Good Luck to ya and God Bless ya.

John T Nordhoff in Indiana

Heres why its not a dead short.

1) First, just consider two 12 volt batteries connected in series with the starter and generator attached to the outer (untied) posts. Neither of those are connected in any way to the tractors frame, both leads go to their windings etc BUT NOT case.

2) Now suppose you take a wire in the mid tie point of the series battery connection and hang it onto a hunk of iron (say like the tractors frame for instance). That in no way affects how the starter or generator function as they are both isolated from any case ground connection. They dont know or care if that center tie is wired to a hunk of iron or your mother in law.

3) Next suppose you took 2 wires hooked to a 12 volt light and ran one wire to an individual + battery post and the other to that same batteries - post, A la, the light would work (fed from that battery only) and not interfere with the starter or generator.

4) Next, since that battery happens to have one of its terminals wired to frame ground, that light would still work if wired to ground and the batteries ungrounded terminal. Likewise, if you hooked another light over to the other batterys outer untied post and ground, it would work also and still not interfere with the other light (fed off other battery) or the start or charge system.

If you just forget about the batteries being wired to to the tractor in the center where they are tied it may be easier to understand. Theres no dead short since neither battery has its + shorted direct over to its -. They both can still feed individual 12 volt loads from their opposite terminals even if one is wired to the frame and they can both still be in series to feed the isolated from frame 24 volt starter.

That help any or make it even more corn fusing lol.

Post back or e mail jmn50@msn.com or call (812) 824-4608 with any more questions n God Bless.

John T Nordhoff in Indiana

~Basically your tractor has 3 electrical systems on it....A 12 volt positive ground system using 1/2 the batteries at positive ground,,, A 12 volt negative ground system using 1/2 the batteries at negative ground,,, & a 24 volt system using all the batteries is series.

~The tractor has an isolated ground 24 volt system, That means that both the starter & generator are completely isolated from the tractor frame [& chassis] so no part of the 24 volt system uses the tractor frame [or chassis] for either a power or a ground circuit. Each of the 12 volt systems DO use the tractor frame [or chassis] to carry power for either power [one 12v side], or ground [other 12v side] circuit.

~The key to that system is a simple little wire running from the 2 [center most] posts between the batteries to the tractor frame. Without that wire the system wouldn’t have either 12 volt system.

~What you have is one 12 volt negative ground system that runs from the positive most battery post in the battery chain to that little wire between the batteries, about ½ the lights & accessories are on that system,,,,, You have one 12 volt positive ground system that runs from the negative most battery post in the battery chain to that little wire between the batteries, that runs the other ½ of the lights & hopefully the other half of the accessories,,,,, You then have a 24 volt system, that runs from the positive most battery post in the battery chain to the negative most battery post in the battery chain [all batteries in series for 24 volts]. Both the generator & starter are electrically isolated from the tractor frame & chassis so the starter is powered from the most positive battery post in the battery chain to the most negative battery post in the battery chain. The generator then charges ALL the batteries together as a 24 volt system from the most positive battery post to the most negative battery post. Simple as that!

~That 12/12/24 volt system is simple & functions extremely well IF all the light & accessories loads are kept even & matched on both 12 volt systems. The problems arise when more accessories are added to one side or other of the 12 volt systems. If electrical loads AREN'T kept pretty well matched then one side of the system doesn’t charge completely & that can spell trouble for starting, as the 24 volt part that uses ALL the batteries in series can’t use the dead battery in the chain & then won’t receive it’s full 24 volts.

~Simple when you think about it.. Difficult when you just think of it…

Questions…JDClooney@aol.com