troubleshooting charging system

[Mike_Lipke]

I think you have a rectifier, which is part of your regulator.
If, after you jump the tractor to get it started, if all is working well with the charging system, you will have 11-12 volts at the battery if it is totally discharged. As it starts to charge, the voltage should rise to 14.6-14.8 volts, or in that area.
The fact that your alternator is putting out 40 volts ac indicates that it is working correctly. Look for wires unhooked, fuses blown, bare wire shorting to frame. These are cheaper fixes. Often happen on diesels because of the vibration.
My sense is that it is your regulator/rectifier, but check input (40vac) and output (over 12vdc) before spending the cake on a new one. Could be wires, or if bad/shorted wires, they could have taken out the regulator, which means you will toast the new one as well.

 

[coloradotrout]

Excellent suggestions... now just this annoyance of a "job" that prevents me from trying them out ;-)

 

[coloradotrout]

the alternator is showing AC volts, and the battery is DC volts, so the "box" in the middle would be converting from AC to DC. Maybe I should just say ac to dc converter ;-) and be safe

Somewhere the AC has to get converted to DC.. I'm pretty sure I have a black box that does that vs that being built into the alternator.

 

[George2615]

What make and model is your tractor? Maybe someone has a similar one. If its a newer unit it probably has an alternator, an older one may have a generator. Most alternators today have the rectifier built in and you can read the DC voltage off the large stud that has the charge wire on it. From your description of replacing the battery and having that one go dead, the alternator (or internal rectifier) isn't working. If thats the case, look in your phone book for alternator rebuilders. They can usually rebuild yours cheaper than you can buy one for.

 

[Mike_Lipke]

An alternator that "puts out" dc voltage has diodes built in that convert the ac to dc. If the diodes are toast, you will get no output, ac or dc.
If you are gettin 40 volts ac at the alternator, that tells me that the alternator is prolly ok. Look for wiring that is open, or a bad regulator/rectumfier.

 

[coloradotrout]

It's a JD4100, year 2000

Tested this eve. Battery is 11v DC (aka dead!). When running, batter is 11v DC (so no charge). Alternator gives 20v AC at low rpm and 50v AC at high rpm. For the life of me I cannot find the AC to DC converter. Those 20-50V AC are with the alternator disconnected from the wiring harness. I don't see a good access pt to measure the Volts under load.

OK, I've got a technical manual, which I'm reading now. I have an alternator - regulator/rectifier. There are also diodes and safety relays in the charging circuit. Looks like I need to pull off the control panel to find those.

 

[Mike_Lipke]

Yup, alternator is good. Find that regulator. If all the wiring is good to and from it, that is the problem. They cost the better part of a bill with Franklin's picture on it.

 

[Mike_Lipke]

BTW, if there is a rectumfier between the alternator and the regulator, check it to see if there is ac current going into it and dc current coming out of it. If there isn't, that is the bad boy here. But I think you are going to find that it is all in one. Your dealer should be able to tell you with a phone call.
Also look for a fuse. Your charge circuit may be protected by a fuse. Hate to see you get rid of a Franklin when you need a 50 cent fuse. Of course, the fuse, if bad, could have blown due to a bad regulator. But you will find that out pretty quick.

 

[Volfandt]

</font><font color="blue" class="small">( For the life of me I cannot find the AC to DC converter. )</font>
It's called a rectifier. Rectifiers convert AC to DC. Inverters convert DC to AC /forums/images/graemlins/wink.gif /forums/images/graemlins/grin.gif

I don't know the specifics of a JD4100 but generally the regulator will have large heat dissapateing fins and be the size of deck of cards or a little larger. They can be mounted under a dash but are generally mounted to frame metal to help dissapate heat. Traceing those alt wires will lead you too it.

Your alternator sounds like it's good. Once you find the reg make sure all connections are good and tight and likes been said check for blown fuses. I wouldn't think that JD used a fusable link between the alt & reg but your manual should indicate so.

Good luck
Volfandt

 

[Marlowe]

It sounds to me like your alternator has an internal rectifier. Lots of automotive units have them internally these days. My little tractor has an internal one.

Tom