Posted by JDseller on December 04, 2011 at 07:45:44 from (208.126.196.144):
In Reply to: 4020 jd batterries posted by j hikemper on December 04, 2011 at 04:46:26:
JD 4020s did not have an ammeter. They had a charging indicator light. If that is what you have there is a diode that you have to remove to get the indicator light to work. To energize the alternator you have to change the wiring that went to the generator/regulator. I also usually remove the voltage regulator. It is not used and is easier to wire around if it is taken off.
Have you taken a volt meter and check to see what voltage is at the batteries when the tractor is running??? A bad alternator can over charge the batteries and that will make them go bad faster. If you have low voltage then the starter usually cranks slow.
I will try to walk you through the wiring changes you need to do. The two wires that went to the circuit breakers on the dash get hooked together. They used to be: one positive ground and the other negative ground. They charged the two batteries to make it 24 volt. These two now provide the wiring that the alternator uses to charge the batteries.
The other wires that went to the regulator are what you use to energize the alternator. Take a volt/ohm meter and find the one that is hot when you turn the key on and off. This one usually had a "L" shaped diode in it. This gets hooked to one side of the alternator. The other factory wires are not used.
To the other terminal on the alternator. You make a short wire that goes under the battery terminal on the alternator on one end. The other end goes to the other small terminal on the alternator.
Most of the time the fuel gauge will need to be changed too. The original one was on the positive ground circuit. It will not work after you change the system over to completely negative ground.
Email me if you need more help. There where several different wiring harnesses used on the JD 4020 24 volt diesels. They where a little different but not much different.
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