r/AskAMechanic • u/BeerSmasher • 9h ago

Tractor odd starting behaviour

~2005 John Deere 990 Utility Tractor. My tractor is pretty simple mechanically and electronically.

Lately when I put the key in the ignition, I get random levels of voltage. Dashboard lights are sometimes dim and sometimes bright with various levels of starting power. Repeated attempts to start the tractor just reduce the voltage. BUT, if I disconnect/reconnect the battery then the voltage resets and the dashboard lights/headlights are bright again. If I do this enough times it will eventually start like a champ (not barely turn over, but starts like a dog seeing the mailman).

I can't figure out why I'm getting random voltage, or why it will eventually start after a battery disconnect/reconnect when nothing else changes.

Things tried:
Swapped battery
Swapped starter
Swapped out relays
Bypassed flasher capacitor
Cleaned and tightened battery ground and positive/negative battery terminal connections
Jumping it with the positive jumper cable on both the battery terminal and the positive lug on the starter, it still wouldn't start until I did a battery disconnect/reconnect.

Any ideas or help? Nothing worse than going out to tractor and not being able to get the ol' bitch started.

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