John Deere LA120

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Old 04-18-13, 04:56 AM
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John Deere LA120

Awhile back I screwed up and reversed the polarity when putting a new battery on my JD LA120 and am now paying the price!

When I started it yesterday morning it fired right up. After using for a short period I had to shut it off. When I tried to restart it the first time I got the clicking sound you usually here when the battery is very low. That's not the case here. Tried it again and this time nothing at all. No clicking or anything else. Hooked the charger up to it for awhile and tried again. Got the clicking again and then it fired up. I left it on while doing all my chores. When I was done I shut it off and immediately tried to restart it again. Again, nothing.

Wondering if I fried the wiring harness when I reversed polarity when putting a new battery in? If that's not the problem, what else might it be? Thanks for your help.
 
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Old 04-18-13, 05:52 AM
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Sounds like it's the alternator's regulator not charging the battery. Its a couple of diodes within the alternator's assembly.
I had a similar problem on a car I use to own. I didn't reverse the battery posts, but had a connection for the alternator brake, which caused some issues with power and took out the regulator.
You might be able to get it rebuilt, or is a full replacement of the alternator.
 
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Old 04-18-13, 09:31 AM
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Sounds a lot to me like you don't have a tight connection at the battery.
 
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Old 04-18-13, 09:35 AM
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Probably be just as cheap to buy a new alternator Northern Mike. I found one in the JD parts catalog for around $45. Is there anyway to confirm its only the alternator or are there other scenarios that might apply? Just don't want to order a new alternator and then find out there might be something else wrong with it. Thanks for your help.
 
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Old 04-18-13, 09:39 AM
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I wish that was the problem cheese but I've checked and all the connections are tight. Thanks
 
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Old 04-18-13, 10:26 AM
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This is based on cars, but should be the same for the tractor.
Check the voltage of the battery when it's not running and then check it again when it's running. If the voltage is less when it's running, you confirmed the alternator.
A car should be 13.5-14.5V while the engine is running. Can't speak specifically of the tractor, but would assume similar
 
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Old 04-18-13, 12:00 PM
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To add to what Northern Mike said, with the voltmeter attached to the pos and neg terminals of the battery, try to start your mower, If the voltage takes a dive ( 2 - 4 volt drop ) then the battery has one or more bad cells.
A new battery is not always a good battery.
 
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Old 04-18-13, 04:43 PM
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If it was on charge a while and still wouldn't start, then suddenly starts, then won't start after immediately shutting it off and trying again, then something besides the alternator is working against you here. The alternator may not be good, but that doesn't explain what is going on here. Check the voltages as mentioned and post with results. Still sounds like a battery or connection problem.
 
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Old 04-19-13, 05:39 AM
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Well, it would have been real easy to just not return to this thread and save myself from embarrassment! But, you were all so helpful and willing to render any assistance possible, I decided to return and be humbled.

It was indeed loose battery cables. I was so sure that I had tightened them down properly when putting the new one in that I would have never thought to check. Must not have got them tightened properly and the vibration from running the tractor eventually loosened them up even further.

Thanks for all the help.
 
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Old 04-19-13, 06:11 AM
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Thank you for the update and letting us know.

Stuff like this happens to the best of us (I've done things like this many times).
 
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