Does any one have any ideas on john deere 120c not charging . Put new alternator in, had it tested and it works as it should on the bench. idiot light is on and only showing 24.1 volts running . what would cause this not to charge .
Have you had your battery tested it's quite possible you could have I shorted cell. Some machines have the diode plus side wired into the hour meter if the hour meter fails you lose your ability to charge. One other thing to look at is whether or not your glow plug control relay is sticking on
I just put new batteries in it . I will take a look at the glow plugs . Hour meter seems to be working fine . Thanks
Oh yeah other thing I can think of is you have a computer controlled voltage regulator possibly and that connection might be dirty. How is your alternator hooked up how many wires And does it have a good clean ground
If.... the new alternator is a chinese copy then it may not have the correct extra parts in it for the system the way the JD works, our 94'hitachi uses the two extra terminals in the back of the alternator for independant voltage outputs to 1.control the idiot light and computer hold power. 2. actual ground feed to the starter for crank interlock. We put in a chinese copy and the idiot light terminal was not connected but other functions worked. Also: did the alt. just quit one day or was there other issues? could be a blown fuse near the main disconnect relay or corroded plug/wires as I have seen it on more than just ours.
There are 4 wires to alt. Main power , dash power on main terminal ,blue wire to exciter terminal and a ground wire to alt. Body. Alternator is made in USA . I checked both fuses by the main disconnect relay cleaned terminals. I am going to look at computer wires . There is no power coming though blue wire to exciter terminal . Not real sure how that wire get to idiot light . I was wondering if it goes through a voltage reg to tell it to turn on and charge?
The old alt burnt . No real fire but it melted all the wires on the alt .
Melting wires on the alt more than likely also melted a weak spot on the same circuit in the machine somewhere.... could be the machine had a short that took the alt out to start with.
Alternator excitation to D+ terminal should come direct from a jumper from the B+ terminal with a resistor in it. The W terminal should be wired to the Alt relay which controls the light in the monitor. Check that wiring real good if there has been melting.