fluctuating ammeter

klink · Mar 3, 2017

my John Deere 520 when the engine is running the tractor ammeter fluctuates radically on both sides of 0. Just bought the tractor and it has a new battery in it. It has all original wiring and still has a 12 volt generator with positive ground. the battery voltage seems be ok, with a hand held digital volt-ohm-amp meter the read out fluctuates when taking a volt reading on the battery. My knowledge tells me its either a bad generator, voltage regulator, amp gauge, or a bad connection. just thought I would see if anyone on this forum might be able to help me out? or someone who might of had a simular problem that they fixed.
klink

jd110 · Mar 5, 2017

Most likely a voltage regulator issue. Possible that you may be able to adjust it if you remove the cover. If not you may need a new one. I would hook a voltmeter up and see if it fluctuates also. If not, it could be the ammeter is bad.

klink · Mar 6, 2017

This JD520 was setting outside for a while { ? } before I bought it, & the battery wouldn't hold a charge, that's why I asked for a brand new battery from the dealer [ I hate to leave anything set outside ] the things I have done so far - I removed the voltage regulator cover and found a lot of moisture & corrosion. I ordered a new voltage regulator and a generator rebuild kit in case I need it now or later. when I turn on the tractor lights with the engine off, the ammeter indicator pointer reads a steady discharge, just like it should. Recapping - before with the engine running the ammeter indicator pointer would fluctuate like a dog wagging it's tail. I think jd110 is right on with the regulator being bad. In my 70 years, I have seen other tractor ammeters act the same way. Anyway I will get it fixed one way or another and I will report back.
klink

klink · Mar 28, 2017

Well, I finally got the parts that I ordered, and got them installed. The problem was the voltage regulator. I also replaced the ammeter just in case. So now with the motor running, the ammeter shows the system is charging. With the motor off and I turn on the lights, it shows a discharge. The generator is in good shape, so I have a generator rebuild kit for future use. I have two tractors that use the exact same generator. Thanks for your help.