1) You have a tractor that everything works. Starting, running, gauges, lights, everything.
2) One day it cranks over very slowly...then click, click, click.
3) You remove battery, install a new one
4) The tractor is dead...100% dead
Ask anyone with an I.Q. greater than a turnip what's wrong.
I mean no disrespect to anyone.
Putting the old battery back in will take you to step 2).
Yes all sorts of things, corrosion, bad connection, etc. can mimic a bad battery, but putting the old battery back at least take you to step 2). Otherwise something wrong with step 3).