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Old 04-03-2017, 08:45 PM   #1
Northwest Outlaw
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Good Alternator not charging...

I'm new to all this wiring stuff, but i have done some research and problem solving. If there is a thread on this already please direct me, i couldn't find what i was looking for.

TRUCK: 1961 with a 1971 small block, using a new '63 front harness because of the alternator hook ups, purchased from ClassicParts.com. The alternator is new.

SITUATION: Alternator is not producing a charge. I've tested this by using a multimeter to read voltage output from the (+) post on the back of the alternator; it reads the same as the battery, about 12v. I've also pulled the negative cable off the battery while truck was running and it died. So, no charge coming from the alternator. I got the same readings while at idle and high rpm.

WHAT I'VE DONE:
1) Tested the alt. at the shop where i purchased it only a few months ago. It's a small mom and pop shop, not a national chain. We tested the alt as well as another one off the shelf and got good readings. So the alternator can produce charge, it just isn't while in my truck.
2) Checked and re-grounded all ground connections, made sure all mounting hardware for the alt brackets, regulator and relay were clean bare metal. Using one 1/2" and one 1" ground strap from the block to the frame, both bolt to bare metal. No change.
3) Replaced the voltage regulator and horn relay. No change.

IDEAS OF THE ISSUE:
-wiring harness is defective and not allowing the regulator to activate the alternator?
-something in the cab wiring is causing interference?
-....i have no other ideas, that's why i'm asking you guys!

I would like to figure this out so i understand what was causing the problem. I know i will hear "Get a single wire alt", but i would really like to know what's up.

Picture is before and after of the front harness, regulator and relay. I can provide more pics of something specific if it will help

Thanks for any help
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Old 04-04-2017, 10:18 AM   #2
VetteVet
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Re: Good Alternator not charging...

At first glance it appears that you have a regulator for a generator which would have come with the 61 charging system.
Your regulator should look like this.

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The harness should have a four wire plug with the following wiring from the ignition switch and the main harness.

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The two end wires on the relay if its labeled, go to the alternator to the plug in on the back labeled R and F.

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The horn relay serves as the main junction for the charging power wires, here's a picture of one, but ignore the words I don't know where they came from.

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Do you have a charging light or did you have the original ammeter.
I'm not quite sure when GM went to the newer style ammeter I think it was 1963.

I hope I have helped but when it comes to mix and match on the early stuff it can be confusing.
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Old 04-04-2017, 02:26 PM   #3
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Re: Good Alternator not charging...

VetteVet thanks, this is the stuff i'm looking for. Clean, simple, well explained diagrams and pictures.

Here is a better picture of my set up, and my parts list:
Harness
Regulator
Relay

I will have to double check everything but i think it's set up the way your diagram shows. The only thing i'm uncertain about is inside the cab, from the firewall connector to the ignition switch. When we hooked it all up and turned the key, the engine cranked so I haven't investigated under the dash too far.

One of the previous owners did some "rewiring" and tried adding an ammeter, but i haven't tried to wire it in yet. I'll try to do some more trouble shooting with this new information and let you know how it goes.

Thanks again
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Old 04-04-2017, 05:19 PM   #4
VetteVet
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Re: Good Alternator not charging...

Ok now I see that you have the correct regulator with the four wire plug in so we can begin troubleshooting. This is the correct wiring for the 63 to 66 charging system and it carries forward into the 67 to 72 in most aspects.

The horn relay is the junction point for the power wires in the system and you need to have the alternator charging wire, a wire from the battery positive post, a wire from the external voltage regulator and a wire to the firewall connector on there. There is also a small 18 gauge wire that connects there and goes into the dash for one side of the ammeter gauge.

If you refer to my diagram of the charging circuit you will see that the brown wire for the regulator comes from the key switch through a light or a resistor and runs to terminal 4 on the regulator. It appears that you have that wired on the regulator correctly. This wire must read 12 volts with the key on in order to excite the fields in the alternator so it can begin charging. This would be a good first check on the no charge problem. I see the ground wire on the regulator to the sheet metal which is also required. It should be grounded to the alternator as well. My picture above shows the ground on the back of the alternator.

The middle wire on the regulator runs to the horn relay junction and that is present also.
The blue and the white wires are on the regulator properly and they run to the alternator gray square plug with the blue to the F and the white to the R terminals.

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The brown wire to the key switch is at the very top of this diagram and it is a resistor wire to the firewall connector where it joins with another brown wire which comes from the dash labeled GEN TELL TALE LIGHT. If you have an ammeter in the dash you will not have this brown wire and the resistance wire will connect to the brown wire on the other side of the firewall connector and that wire is the wire to the regulator. Remember you need to see 12 volts on this wire in order for the alternator to charge.


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Post back with results. VV






























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Old 04-04-2017, 05:49 PM   #5
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Re: Good Alternator not charging...

Again, this is good stuff. Thanks! I'll be sure to let you know how things go when I get a chance to run through these diagrams to make sure I got everything needed and do the tests.
As far as the Alt wiring to the Regulator it is all as you've said it should be. I had pulled those last wiring schematics earlier to use, but haven't gone inside the cab to make sure all is well in there.
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Old 04-09-2017, 12:59 AM   #6
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Re: Good Alternator not charging...

Made some progress, but not sure exactly what it means...
One of the differences in the 63 harness and the 61 cab wiring is that there isn't a resistance wire for the Regulator. The brown wire from the regulator was going to a blank slot in the firewall plug, at least in my truck. The P.O. had done some interesting reworking. I filled the slot with a blade connector and ran a wire to the IGN post on the Ignition. When I turn the key to ON, the regulator started to smoke. I didn't get a chance to test if I was getting a charge as it was just me in the garage and I wasn't comfortable running the engine with the smoking regulator.
I've drawn my wiring diagram.
Thoughts?
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Old 04-09-2017, 11:42 AM   #7
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Re: Good Alternator not charging...

Wire from battery should be on same terminal as the alternator and regulator
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Old 04-09-2017, 10:51 PM   #8
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Re: Good Alternator not charging...

So after thinking about it I decided to go ahead and get the single wire alternator. I was glad to figure out where my issue was, not having the resistance circuit for the regulator, but didn't want to piece together the solution since I plan on cleaning up the dash wiring mess at some point.
The new alternator is working like a champ, battery reads 14.6-7v. I cut out the unnecessary wires from the harness and cleaned it all up.
Thanks for the help VetteVet
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Old 04-09-2017, 11:15 PM   #9
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Re: Good Alternator not charging...

My pleasure, sometimes the easy way out is the best way. Some of these one-wire alternators can be used as a one-wire or a three wire. But if you're happy I'm happy.
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Old 04-10-2017, 01:15 AM   #10
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Re: Good Alternator not charging...

http://www.madelectrical.com/electri...reewire2.shtml this article says why a one wire isnt that good, although I have a one wire on my 74K20 and havent had any problems, very confusing,I am going to install a three wire internal regulated alternator in my 72K20
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Old 04-10-2017, 03:04 PM   #11
Northwest Outlaw
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Re: Good Alternator not charging...

Quote:
Originally Posted by VetteVet View Post
My pleasure, sometimes the easy way out is the best way. Some of these one-wire alternators can be used as a one-wire or a three wire. But if you're happy I'm happy.
I'm really glad to have gone through the exercise and learn the charging system better. thanks again

Quote:
Originally Posted by El Dorado Jim View Post
http://www.madelectrical.com/electri...reewire2.shtml this article says why a one wire isnt that good, although I have a one wire on my 74K20 and havent had any problems, very confusing,I am going to install a three wire internal regulated alternator in my 72K20
That article is very hard to follow, the writing isn't very straight forward with the Pros and Cons of either the 1 or 3 Wire Internally Regulated Alternators. All i got from it was that the 3-wire has the possibility for some indicators?
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