Hello:
I have been trying to troubleshoot an electrical problem on my tractor (John Deere 300 with 16 hp Kohler single cylinder) and so far I am totally stumped. The problem is this: The battery seemed to be out of juice so I had to jump the tractor from my car. The tractor started right up and ran.... but as soon as I disconnected the jumper cables from the car, the tractor stalled immediately.
I am assuming the tractor should continue to run on its own power, so I started testing the charging system on it. The stator voltage was fine, around 30 volts AC. However when I went to check the voltage coming out of the rectifier, my multimeter went crazy and I could not get any consistent reading when connecting the negative of the multimeter to the engine block. It was as if something was interfering with the multimeter. But when I used the frame of the tractor for the negative, I finally got a consistent reading of around 0.3-0.7 volts DC. The negative battery terminal runs directly to the engine block and that connection was good. So immediately I assumed the rectifier was bad. After connecting a new rectifier still the same problem.
So next I hooked up the jumper cables again and shut off the car, keeping the cables attached.. and the tractor continued to run just fine. I checked the voltage across the tractor's battery and it was around 14.5 volts. I shut off the tractor with the key and the voltage dropped to around 13.5 volts. When I saw this I assumed the charging system was working and that my earlier assumption of a bad rectifier was incorrect. Then I removed the jumper cables and the voltage then showed 10.5 volts. Is it possible that the tractor's battery is bad or shorted, causing these issues???
Thanks in advance for any feedback...
-- Chris