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M3 charging system
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plummerscarin View Drop Down
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Joined: 22 Jun 2015
Location: ia
Points: 3826 		Post Options Post Options   Thanks (0) Thanks(0)   Quote plummerscarin Quote  Post ReplyReply Direct Link To This Post Topic: M3 charging system
    Posted: 15 Nov 2016 at 9:04pm
Fired up the M3 to pick corn yesterday and the alternator didn't seem to want to charge the batteries. Removed alt, took it in to be tested and only putting out 11 volts. Installed replacement unit and still no charging. Pulled one out of the other M3 that worked fine when combining beans and IT wont work either. After reading the book I tried a few checks to see what else might be wrong. The green output and blue volt sensor wire show 12 volts. The yellow exciter wire is 0 with key off and 2.4 volts with key on. That wire has an inline resistor. Is this normal? Am I missing something else? Your thoughts will be greatly appreciated,thanks.
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DougS View Drop Down
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Joined: 03 Nov 2011
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Points: 2490 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 15 Nov 2016 at 9:07pm
The exciter wire should have 12 volts on it with the ignition turned on.

Check for a blown fuse, wring problem such as a loose connection, corroded terminal, bad ignition switch, etc. I doubt the problem is in the alternator unless the original alternator has a problem and blew a fuse.



Edited by DougS - 16 Nov 2016 at 5:37am
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plummerscarin View Drop Down
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Points: 3826 		Post Options Post Options   Thanks (0) Thanks(0)   Quote plummerscarin Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov 2016 at 8:03pm
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plummerscarin View Drop Down
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Points: 3826 		Post Options Post Options   Thanks (0) Thanks(0)   Quote plummerscarin Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov 2016 at 8:11pm
Update:
I had considered the possibility of loose connector in the harness or possibly a short so after I got home from work I went to check and found that my uncle took it for a spin during the daylight. After while the voltage came up to 14 and now can run with the lights on. Didn't get to test exciter wire yet but I'm thinkin that a short could could be suspect? Thanks for the help Doug and I'll keep updating.
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Kevin in WA View Drop Down
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Points: 612 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Kevin in WA Quote  Post ReplyReply Direct Link To This Post Posted: 16 Nov 2016 at 9:45pm
Could be that the alternator self started on its own at high rpm when your uncle drove it and that the exciter wire is still low on voltage.
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DougS View Drop Down
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Points: 2490 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 17 Nov 2016 at 5:02am
Probably what happened there, Kevin.
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plummerscarin View Drop Down
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Points: 3826 		Post Options Post Options   Thanks (0) Thanks(0)   Quote plummerscarin Quote  Post ReplyReply Direct Link To This Post Posted: 17 Nov 2016 at 8:32pm
Got back out to it tonight. Uncle ran it for a while before I got there and it never kicked on for him. Checked the voltage again and it was up to 6 volts. Pulled the access panel off the cab and have 12 volts off the ignition switch. Wiggled some wires and harness around and got the exciter up to 10 volts (exciting!). Fired up the machine but still not charging until I took a short piece of fence wire and touched it from the power to fuel solenoid and exciter wire terminal.That got the alternator to go. 
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DougS View Drop Down
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Points: 2490 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 18 Nov 2016 at 9:03am
Go back to my original post. Check the items I mentioned. Beware of voltage readings that are made in an open circuit. This smells like a loose connection or corroded wire at a terminal or splice.
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