580sl series 2

I have a 2001 580 sl series 2, 4wd, 4n1 and I love it. I'm retired now and it's the only backhoe I kept but now it's giving me a few small problems, it won't charge and the tach stopped working. It has a fairly new Case alternator that's got about 800-1000 hours on it. About 3 months ago the my battery slowly went dead so I replaced it. Well, it wasn't the battery because it's still doing the same thing. But, all of a sudden a few weeks ago it started charging and the tach started working, but it didn't last longer than a week though. The amp gauge doesn't even flicker while it's running but when the alternator was working during that short week it showed about 14 volts. I've done the quick checks like alternator plug, then took the dash out and everything looked decent although a little dusty/dirty. I have a complete maintenance/parts manual but it hasn't helped. I know there's an exciter wire, diode and connectors but I need help with a direction. Case told me to check the alternator output (at least 10 volts) and then move backwards from there, but I'm not sure what that meant so it didn't help much. Any quick fix ideas out there? I have read posts in this forum but most were about older backhoes with some problems being close to what I'm having. I'm usually fairly good with this kind of stuff but at 65 things aren't so easy anymore. Thanks