420c Alternator issues

General help and support for your Lindeman through 2010 John Deere crawler
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E.Huffman
440 crawler
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420c Alternator issues

Post by E.Huffman » Fri Mar 05, 2021 9:26 pm

Hi so I just replaced my generator with an alternator ( it was converted to 12 v before i got it and they just disconnected the junk generator :evil: )And I put a gm 1 wire alternator on and It seems the volts fluctuate from 17 to 14 volts the higher the crawler rpms the less it fluctuates... Also it is not charging my battery... Am I missing something or is it a new defective alternator? Thanks!

Jim B
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Re: 420c Alternator issues

Post by Jim B » Fri Mar 05, 2021 9:51 pm

With that voltage at the alternator it should be charging the battery. But you don't say where you are checking the voltage. If you are checking at the alternator, what is the voltage across the battery terminals? 12 volt negative ground? One wire (10 gauge recommended) from alternator battery terminal to the ammeter? Second terminal of the ammeter wired to the battery cable stud on the starter? Old ammeter or new one (higher scale to match the alternator)? If no ammeter, then the battery terminal of the alternator wires direct to the battery cable stud on the starter. Just some thoughts of things to check, not knowing how you wired it.

Billhc83
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Re: 420c Alternator issues

Post by Billhc83 » Sat Mar 06, 2021 3:59 am

I just did one using this as a reference, seemed to work.
http://photos.yesterdaystractors.com/ga ... 188502.jpg

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E.Huffman
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Joined: Sat Nov 14, 2020 6:33 pm
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Re: 420c Alternator issues

Post by E.Huffman » Sat Mar 06, 2021 6:51 am

Jim, It has an old anmeter that shows a negative with the lights on but no postive when it is running. I have the wire running from alternator to ammeter and then from ammeter to battery. Yes all 12v negative ground. Is there is a reason it is fluctuating real fast? The volts I mean?

Jim B
350 crawler
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Joined: Sun Nov 05, 2017 11:36 am
Location: western Maine

Re: 420c Alternator issues

Post by Jim B » Sat Mar 06, 2021 7:47 am

All new wires? All the old generator and regulator wires discontinued or removed? Does the alternator have a ground terminal on it? Even though it should ground through the case try running a jumper wire from the ground terminal to the battery ground post. Eliminate the possibility of excess resistance somewhere on the ground side.

At the ammeter, is only the wire to the battery on one terminal and the wire from the alternator on the other terminal along, with the wire to the switch and any other power wires?

What are you using for a test meter? Where are you checking the voltage? What is the voltage across the battery terminals when it is running? If you are checking voltage at the alternator, some digital multimeters are affected by "electrical noise" from the ignition system and read erratically, when used near the ignition system of a running engine.

There could be a problem with the alternator, but I would want it tested on a test stand before condemning it, especially since your ammeter isn't reading correctly. If the ammeter is wired correctly and not showing charge when running, I would start by replacing the ammeter. (Personally, I would have replaced the ammeter with at least a new 60-0-60 one when installing the alternator. Or, I have been changing from ammeters to a voltmeters, I think the voltmeter gives a better idea of the state of the battery charge.)

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E.Huffman
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Posts: 149
Joined: Sat Nov 14, 2020 6:33 pm
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Re: 420c Alternator issues

Post by E.Huffman » Mon Mar 15, 2021 6:45 am

It turns out all my issue was bad connections....

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