JD990 Charging issue

[ssgp2]

I thought I would share a solution that worked for me regarding my 990 not charging.
Took the alternator apart and cleaned it with a toothbrush (was packed full of dirt). This was a very easy job and may need to be a regular maintenance issue, at least maybe every 200 to 400 hours. This type of permanent magnet alternator is used on many different tractors.
What led me to take this thing apart was I had a job to do first thing in the morning and went to load the night before and the battery was dead. I jumped it with the truck, but died a couple of minutes after taking the cables off. Battery tested bad (it was about 12 years old), so I put a new one on and cleaned the cables and terminals. Wandering if there were other issues, I pulled the neg. terminal to see if it would stay running, but it died. Reconnected and restarted, but this time I disconnected the alternator plug and it stayed running and the battery/charge indicator light came on. Went to https://partscatalog.deere.com/jdrc/ to see if i could get a part number, price and availability and noticed that replacement parts for the alternator itself were available, so I took it apart to see if something looked burnt or otherwise not right. That's when I found it was caked with dirt inside. Cleaned it with a toothbrush and lightly sanded the magnets with 200 grit sandpaper. Put it all back together, restarted and pulled the neg. cable and she stayed running and no battery/charging light. Been a couple of months now and no issues. Just thought I would share incase someone else could be helped.

 

[bmaverick]

Actually the JD990 is a Yanmar. That's a very common Yanmar alternator off of a Nissan-Datsun from 1973-1996. And the thing really isn't an alternator, it's really a dynamo.

Anyone can walk into AutoZone or other auto parts store and order these. Typically these come with a 1-yr/12,000 mile warranty.

Now the OE for Yanmar/Deere is Kuksan-Denki.

 

[Tinhack]

Those aren't Yanmar exclusives. I had one on my Kubota. I replaced it and the controller with a "real" 40A alternator. I used a Mitsubishi alternator from an old 86 Justy because of it's compact size.