4020 12v/24v system

Gerald J.

Nowwwww to get 12 volts to operate the lights etc, its still 12 volts from EITHER outermost untied battery post (+ of one - of other) with respect to frame ground, its just that one battery supples 12 volts Negative ground while the other supples 12 volts Positive ground. Those 2 circuits feed up to the light switch and are identified as either A or B circuits and the theory was to balance the loads on the batteries by supplying some lights off the A circuit (one battery) and others off the B circuit (the other battery).

The charging system is 24 volts also isolated from frame ground and charges the 24 volts across the outermost two untied battery posts (+ of one battery - of other) charging the series battery combination both at once.

It happens inside starters that copper brush dust can cause a shorted connection from one of the batteries to frame ground (its supposed to be totally isolated from frame) which can discharge them and its also difficult to keep the loads balanced causing one battery to have to work harder then the other.

When asked about problems with 6 or 12 volt grounded systems like most other tractors we can often help over the net, buttttt ttt your system is too complicated to provide as much help not being there armed with a test lamp and meter, sorry..... ..

As far as charging either battery, you still connect + to + and - to - from a 12 volt charger to either battery, its just that you find on one of the batteries has its - tied to frame and the other has its + tied to frame. Thats the inner tie point which makes up the series connection. Still, its 12 volts from either outermost untied battery post to frame ground, which is how n where n why 12 volt lights or other 12 volt loads worked when fed from the A or B circuits fed up to the light switch. Due to unbalances one batery can run down and if either is bad that seriously affects starting operformance as you are experiencing. Its also best if both batteries are equal in rating and age and condition and often BOTH have to be replaced if one is bad cuz the other one would then be weaker as its older.

Best wishes

John T

This being said I am becoming less and less of a fan of this system.

What is the recommendation and what is involved in changing this 24 volt positive ground to something a little more user friendly. I would assume the starter needs changed to 12 volt, the generator to an altinator, and the battery cables replaced. What about the gauges and lights if I was to change to a 12 volt negative ground with two batteries??

Does John Deere make a kit to change this system?? I am just trying to learn as much as I can before I decide to change the system and blow something up.

Thanks

On the light switch where the two A and B circuit BAT inputs were, they would be tied together with now only one 12 volt + battery source (from where both + are tied in paralell). The lights arent that complicated to change over as they were already for 12 volts its just that some were on the A battery and others the B, but now those are tied and common from ONLY the paralell + 12 volt combination. The gauges may or may not be tricky, but if they were originally configured as 12 volts negative ground (i.e. were fed ONLY from the Negative grounded battery) then they woulndt be any problem.

NOTE Im NOT a New Generation guy and have never done of of these but am knee deep in theory to explain how n why, but you really need to talk to someone who has done this before as far as cost and how much trouble or how complicated it all was !!!!! !!!!! !!!!! ! Buick n Deere and Gerald J and others are wayyyyy more familair with 24 volts and conversions then I would be

Best wishes n good luck, let us all know how it turns out.

John T

It comes with a 12 volt starter, 12 volt alternator and bracket, and instructions. No doubt there is some wiring, though beyond the battery cables to parallel the 12 volt batteries (or use two 6 volt in series like some later tractors) the load wiring should only require hooking the A and B sources to the battery positive.

I think the shop manual shows 12 volt wiring diagrams for the diesels because they came from the factory that way when equipped with a cab.

Gerald J.

I would assume the generator has a voltage regulator somewhere that would need to be removed in favor of a nice delco altinator with an internal regulator.

If you NEED to, or are simply DETERMINED to change it over to 12-Volts, email me, and I will get a diagram to you.

It's quite simple. They use a 12-Volt starter, and an additional solenoid to interface between the key switch and neutral start switch(s)and the solenoid on the starter. A simple Delco 10SI alternator is used.

Cost-wise, you don't NEED a $600.00 kit.

The starter is the main expense, they can be found at rebuilders, etc., for less than Mother Green's price, and the 12-Volt alternator can be had for as little as about $10.00 at a auto salvage yard, to as much as $150.00 for a rebuilt at Deere.

One "issue" is the fuel gauge. It is now supplied from the (+) grounded half of the 24-Volt system, and will be inaccurate on the new 12-Volt (-) ground system. If more accuracy is needed, you'll have to get a gauge, and POSSIBLY a sended for a newer 12-Volt 4020.

bigcoulee@hotmail.com

Gerald J.

From what you described it sounds like a really bad idea to hook any extra 12v device to that system.

The design is just too complicated - having to worry about balancing everything. Alternating the gandy box on every row between positive and negitive ground ? or the right is positive and left negitive.

A better way would be to use a really heavy duty resistor to drop the 24v to 12v.

Is there any advantage to this crazy system, I can see this being a real problem running negative ground equipment on it and running a danger of shorting something out. Is there an easy way to change the system to a 12 volt negative ground system with two 12 volt batteries?? I would assume you would have to change the starter and rearrange the battery cables, but is there anything else that would get messed up??

It's NOT really (+) OR (-) ground.

The midpoint of the system is grounded to the chassis, making 1/2 of the system 12-Volts (+) ground, and the other 1/2 12-Volts (-) ground.

Of course, the older John Deeres (I have an A like this, anyway) were positive-ground. So I can't give a straight answer here. But I suspect in the later models that they would've changed to the more common negative-ground configuration.

Could it be a starter problem? Well, I have an IH 756 with similar behavior. I'm told it could be either bad brushes or a solenoid problem. So, yes, it can be a starter problem. Or it could be a wiring problem. I've seen that a few times, particularly with tractors with a more than a few years on 'em. I like to replace the wiring on my tractors once they start acting up like this.

Just a few thoughts, from one of the 'newbies' on this board. :)

There is NO "relay would switch the 2-12v or 4-6v batteries from the normal 12v operation to all in series for 24v to the starter, then switch back to 12v when releasing the start button" used in the Deere system. The batteries are ALWAYS in series, delivering 24-Volts to the starter, and being charged at 24-Volts.

You are obviously thinking of semi trucks and construction equipment that used a series-parallel switch. The Deere system did NOT use a series-parallel switch!

As an IH guy, you are missing a TREAT, not realizing Deere/Delco came up with a split 24-Volt-12-Volt system for the diesels from the late '50's to the mid-to-late 60's

Nick's correct.

It IS a 24-Volt system. The midpoint of the two batteries is grounded to the chassis, giving (+) 12-Volts for 1/2 of the lights, and (-) 12-Volts for the other 1/2 of the lights.

This system worked GREAT for it's era, but nowadays, trying to operate lots of 12-Volt (-) ground accesories can cause problems with the charging system providing enough current to run the (-) ground loads, as it charges both the (+) ground battery and the (-) ground battery in
series.

nick,

What is the CCA rating of the batteries? Are they both fully charged when you atempt to crank the engine?

The currently-recommended battery is #TY24341, with 620 CCA's.

Gerald J.