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Old 08-18-2021, 09:27 AM   #1
lukbrw
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Single wire alternator not charge

Looking to get some advice on a charging system. previous owner did the single wire upgrade to the 64 c20 that we picked up. All the wiring looks correct and there is a resistor under the dash that is lighting up with no issues. Everywhere we test we only get 12.4v going back to the battery.

Replaced a few ends and cleaned up the terminals but no change.

Alternator was bench tested at Oreilly's with no issues.

Brown, blue, and white wires that went to the old external regulator are not connected to anything as described in previous posts.

We put in a new battery, but the old battery had the same amount of voltage.

Any suggestions on something that needs to change or check?

Thanks!
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Old 08-18-2021, 11:04 AM   #2
The Rocknrod
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Re: Single wire alternator not charge

While it's running the alternator power wire should be seeing between 13.8 and 14.2 volts. I have heard the 1 wire alternators require the engine to reach 1000 or 1200rpm before the alternator will start to charge?
I would let me move this to the electrical section also. https://67-72chevytrucks.com/vboard/...splay.php?f=64

Last edited by The Rocknrod; 08-18-2021 at 11:17 AM.
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Old 08-18-2021, 04:10 PM   #3
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Re: Single wire alternator not charge

I do see a couple of threads now stating it needs to be over 1000 rpm to charge.....something I wasn't aware of.

We did increase the motor speed multiple times with no change.
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Old 08-19-2021, 07:59 AM   #4
lukbrw
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64 c20 Single wire Alternator not charging

Looking to get some advice on a charging system. previous owner did the single wire upgrade to the 64 c20 that we picked up. All the wiring looks correct and there is a resistor under the dash that is lighting up with no issues. Everywhere we test we only get 12.4v going back to the battery.

Replaced a few ends and cleaned up the terminals but no change.

Alternator was bench tested at Oreilly's with no issues.

Brown, blue, and white wires that went to the old external regulator are not connected to anything as described in previous posts.

We put in a new battery, but the old battery had the same amount of voltage.

Any suggestions on something that needs to change or check?
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Old 08-19-2021, 08:31 AM   #5
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Re: 64 c20 Single wire Alternator not charging

Could the issue be that the previous owner connected the red lead directly to the power output on the back of the alternator instead of going to the junction on the core support?
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Old 08-19-2021, 10:56 PM   #6
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Re: 64 c20 Single wire Alternator not charging

A true 1 wire alt doesn't need that white 2 wire connector. If yours does, then it is a standard alternator. Try running the red voltage sense wire to the junction box(if present) or to the battery. Yes, that means you will have both red wires going to the same place but that is how the 10/12 SI internal regulated alternators are designed. The red voltage sense wire picks up the voltage from where it is connected and adjusts the output of the alt to reach the desired voltage at that location. This lets it cancel out any voltage losses in the main charging wire.
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Old 08-20-2021, 08:23 AM   #7
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Re: 64 c20 Single wire Alternator not charging

Thanks! Will give that a try.
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Old 08-20-2021, 03:30 PM   #8
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Re: Single wire alternator not charge

When I installed mine there was a plug that used to connect to the external regulator. When the regulator was removed I had to install a cap on that plug that rerouted the wires. It looks like a lot of those wires on your truck were cut instead. I don't know that those wires were for but it might be something you might want to look into.
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Old 08-21-2021, 07:27 AM   #9
bob arrington
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Re: 64 c20 Single wire Alternator not charging

the white wire in that plug makes the alternator start charging immediately instead of having to hit 1000 rpms to start charging, if it were mine, and it was cause I just went thru this with a newly installed 160 amp , Id double check the ground, over time you will like the instant charge function that that white wire provides
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Old 08-21-2021, 10:30 AM   #10
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Re: Single wire alternator not charge

Quote:
Originally Posted by The Rocknrod View Post
While it's running the alternator power wire should be seeing between 13.8 and 14.2 volts. I have heard the 1 wire alternators require the engine to reach 1000 or 1200rpm before the alternator will start to charge?
I would let me move this to the electrical section also. https://67-72chevytrucks.com/vboard/...splay.php?f=64
Rocknrod is correct on the rpm statement, sometimes a bit more depending on the rebuild….some of your wiring looks questionable, cut, spliced , taped up…a little corrosion will not help you in any way, that yellow crimp on terminal is not sealed, stuff like that will wreak havoc on voltage…
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Old 08-21-2021, 01:48 PM   #11
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Re: 64 c20 Single wire Alternator not charging

Ran the red wire coming out of the battery and still only getting 12.43 v coming out of the alternator and at the battery. Will start taking more apart but assuming doming isn’t causing the regulator to send voltage.

Thoughts?
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Old 08-21-2021, 05:46 PM   #12
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Re: Single wire alternator not charge

Just out of curiosity what would be the alternative to the yellow crimped on terminal? Does it need to be soldered and shrink tubing applied?
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Old 08-21-2021, 06:43 PM   #13
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Re: Single wire alternator not charge

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Just out of curiosity what would be the alternative to the yellow crimped on terminal? Does it need to be soldered and shrink tubing applied?
Wire becomes brittle at the soldered joint, and will break at that point, this per a study by BMW…I use a quality crimper on a non insulated terminal…then I use a double wall(thicker) heat shrink that is adhesive lined. The Klien crimper i use stakes the wire in the terminal, not just squeezes it. That’s just how I do it, surely there are other methods, but this works for me, never have any issues…
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Old 08-21-2021, 09:12 PM   #14
lukbrw
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Re: Single wire alternator not charge

Redid all of the terminals and validated everything was correct and now it’s charging under acceleration. Thanks for all the input.
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Old 08-22-2021, 07:10 AM   #15
The Rocknrod
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Re: Single wire alternator not charge

Glad to hear it.
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Old 08-22-2021, 07:59 AM   #16
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Re: 64 c20 Single wire Alternator not charging

Go to the home page of this forum and check my Electrical Faqs and look at the threads on
converting to an internal regulated alternator. Also look at the thread on why won't my battery charge.
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Old 08-22-2021, 11:03 AM   #17
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Re: 64 c20 Single wire Alternator not charging

Replaced a few wires and connections. Battery is now charging under acceleration! Thanks for the advice.
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