John Deere 4440 Charging Problem

[BSeyler]

My JD 4440 quit charging a few days ago. I took the alternator to a rebuild shop and picked it up this afternoon. While it was gone, I slow charged the batteries (they were almost dead) until my hydrometer showed them to be charged and they passed a load test. After installation, I started the tractor and got a reading of 13.75 volts on the positive post of the alternator and the gauge in the cab showed well into the green. (I wish they'd just put numbers on them!) I left it running and put my tools away. When I got in the cab to shut it down, my gauge showed lower voltage, so I put my meter on the alternator and it's only showing 12.5 volts. When I turn the work lights on, it shows into the red on the gauge. The belts are tight, as are all connections. Thoughts?

 

[NIsaacs]

Does the dash have a alternator light? Some systems use that bulb as a fuse on the exciter wire to the field. Ignition on, engine off, the bulb is lit, when it starts and charges the bulb goes off. If no dash light, does the alternator have/use a field wire? If so, is it hot when ignition is on?

 

[BSeyler]

 

[BSeyler]

 

[BSeyler]

Nick,
Here are a couple of pictures of what I have. I’m a little out of my element on this. thanks, Bud

 

[NIsaacs]

That looks just like my Ford/Cummins. The big green is battery power as is the smaller white one on the two wire plug. I think the small wire in the plug is hot with the ignition on, cold with it off. I will test mine in the morning if you haven't fixed it by then.

 

[BSeyler]

Thanks, Nick!
With the ignition on or off, the small wire shows 12.7, the same as the batteries. Large wire 12.1 when running, 0 when not running. I’ve cleaned and checked connections without any change.
Edit
By large wire, I meant the larger of the two in the plug. The large single wire goes to the batteries.

 

[AH64ID]

Where is the voltage regulator? Is that where the big wire on the pair goes?

 

[BSeyler]

Internal regulator, from what I understand from looking at Yesterday’s Tractors.

 

[AH64ID]

So where do those two smaller wires go?

 

[BSeyler]

Not sure where they end up. They go up and run along the hood toward the cab and I’m not sure where they end up. I may take the alternator back and let them test it in the morning. That should point to the next step. If it checks out, I need to locate a service manual so I don’t start down a rabbit hole.

 

[AH64ID]

Windings or regulator are most likely, but it could also be the sense voltage wire that is failing.

 

[BSeyler]

Thanks! Since it worked for a few minutes (13.75V), I wonder if the new regulator they installed is one of those “high quality “ chicomm goodies. I’m going to take it off in the morning and have it tested. Process of elimination, I guess. Maybe a loose connection? Anything is possible on a 43 year old machine.

 

[GCroyle]

I like the idea, get it tested.

 

[Mark31]

Twenty+ years ago, my 4440 did the same thing. There is an electrical something-or-other up above the starter on the firewall that was bad. Replaced it and all was well.

 

[NIsaacs]

That looks just like my Ford/Cummins. The big green is battery power as is the smaller white one on the two wire plug. I think the small wire in the plug is hot with the ignition on, cold with it off. I will test mine in the morning if you haven't fixed it by then.

Humm, now I don't know what to think. On my Ford, both small wires power up with the ignition. Maybe like Mark said, something is powering up the one small wire but shouldn't? If so, maybe it cooked the regulator again? Not much help here, Lol.

 

[mwilson]

Stole a couple minutes to look into this, two things...

(1) There is a rectifier shown in the parts breakdown.....I don't have time to dig into the theory..

(2) Sometimes equipment electrical functions depend on an oil pressure switch that makes contact under pressure so that hourmeters, etc. don't run when the key is left on...that could affect other electrical stuff depending on the Running Deere engineer's outlook on life...

Parts Book Here...all set up for you..hit the link below and you go right into the 4440..


https://partscatalog.deere.com/jdrc...JT04sMjg0NzojQ0FUQUxPRyw3NDM2OTpFUVVJUE1FTlRd

 

[mwilson]

A similar issue on a 4240..

https://www.tractorbynet.com/forums/threads/jd-4240-charging-sysm-not-working.381336/

 

[NIsaacs]

Mike might be on to something. This is a generic wiring diagram of the dash light I was talking about.

https://smithcoelectric.com/blogs/tech/common-10si-12si-15si-17si-21si-22si-wiring-diagram

 

[BSeyler]

I took the alternator back to the shop this morning. The owner took it back to the shop to check it out and had it figured out before he even got to the bench. There is a screw on the brush holder that didn’t get tightened and he could feel a rough place when turning it by hand. About ten minutes on the bench and then a spin test and I’m in business. Luckily, it hadn’t run enough to cause damage. He was highly embarrassed and very apologetic. This shop has been around for many years and they have an excellent reputation. The farmer I work for some has quite a number of trucks, tractors, combines, etc., and has had good work from them. I’m going to chalk this one up as an oops. Thanks for all of the help and ideas! TDR people truly are the best!
Bud