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Old 06-02-2017, 12:10 PM   #1
AlbertaClassic
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81 Wiring Alternator Help

Hello, I am new to this part of the forum. I recently purchased my first squarebody, an 81 GMC K2500. Due to a recent sale of my DD, I am in a hurry to get this thing running consistently. I have killed a battery or 2 (I'm not very mechanically inclined, but learning) and have done the voltage tests on the battery and have confirmed the battery isn't getting any charge. Atleast up to 2500 RPMs. So I need a quick fix to get the alternator running. It looks like to me that the battery charge post (?) on the alternator isn't connected to anything. See attached photo below. There is a loose red wire just hanging there. In theory if I hook that back up it should work correctly, no? Or, for now would it be possible to run a 10-12 gauge wire from the battery post straight to the alternator? Should I fuse it? I apologize if this should be in electrical, I'm just hoping to get it sorted out. Thanks in advance.
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Old 06-02-2017, 01:53 PM   #2
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Re: 81 Wiring Alternator Help

There supposed to be a wire with a ring terminal on the stud on the back of the alternator
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Old 06-02-2017, 02:26 PM   #3
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Re: 81 Wiring Alternator Help

Like this..its a heavy wire about 10ga or so..
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Old 06-02-2017, 04:09 PM   #4
AlbertaClassic
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Re: 81 Wiring Alternator Help

Okay. So I have a wire that's there, theoretically if I hook it up I should be good to go? If the harness is a little butchered, what would be the best way to go about hooking it up to the battery? Would a direct line work? Thanks
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Old 06-02-2017, 07:08 PM   #5
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Re: 81 Wiring Alternator Help

My alternator wire goes to the 2 pole junction block at the center of the firewall above the distributor
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Old 06-02-2017, 07:30 PM   #6
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Re: 81 Wiring Alternator Help

If you are talking about that red wire in your first pic with all the tape on it, probably yes. The other end of that wire should run to the junction point on your firewall. Same place as the red wire in the two wire connector on the alt.

Disconnect the battery when you test your hookup since IF that red wire is the wire that is supposed to be connected to the alt, it is full hot even if the ignition is off.
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Old 06-03-2017, 10:27 PM   #7
AlbertaClassic
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The wire that was there was through the junction to the battery. Everything is good to go and I'm at 14.5 amps at idle now. Thanks for all your help
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Old 06-03-2017, 10:30 PM   #8
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Re: 81 Wiring Alternator Help

Volts*
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