john deere 624g starting system

hi all, just recently purchased a 90s 624g deere. very odd thing going on. it starts sometimes and other times starter wont engage at all. In times like this, I try to jump the starter directly with screw driver and still nothing. I had starter rebuilt and everything checked out fine. batteries good, connections and cables all good. its the weirdest thing. Another issue thats possibly irrelevant is the alternator light stays on in the cab on on dash. I had alternator rebuilt as well and the system is charging fine. any thoughts?

If you jumped right at the starter (which you should never do by the way) and it did not crank either your starter solenoid is bad or your positive cable/ground is bad. Also could be a bad battery. Were the batteries load tested? How did you determine your cables were good. With a meter or visually? I think the engine and batteries are both grounded to the frame on that model. Check to make sure the engine is solidly grounded to the frame and that the batteries are also solidly grounded to the frame. May have to perform a voltage drop check of the positive cables and ground to find the problem. Do you know how to do that?