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BruceJ Samba Member
Joined: June 16, 2009 Posts: 260 Location: Portland, ME
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Posted: Tue May 06, 2025 3:24 pm Post subject: Need VR/Alt wiring help '72 |
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1972 Bus. Motor was out for rebuild. I re-installed it today. No issues except this wiring question.
I replaced the alternator harness as the old one was crusty. The new one did not include the black wire that formerly went to the "test network" and that's fine by me. I tossed the old harness but I'm pretty sure there was no black wire on that one either (more on this later).
Before I pulled the motor I was pretty diligent about labeling things. But now I'm not so sure.
The paired wires at the one connector (one is green and yellow, the other appears a dull greenish-blue) I'd labeled "to green wire". Now I'm wondering, what the heck? Looking at my wiring diagram (Bentley) and around my engine room, I don't see a green wire that would make a logical connection. I'm also thinking the blue wire from the alternator harness should be connected to those paired wires (and not the black wire, which I could have sworn was the way it was hooked up before), and that maybe the black wire had to do with the old test network. Except the black wire here appears to run into the harness up front. And though my Bentley shows a the blue wire splitting at the connector--one goes up front, and one to the blower relay--the wire that I have going to the relay is green and yellow, versus the blue shown in the diagram.
(Side note: The blower has never worked since I owned the Bus, but I didn't mind it. As a curiosity, I bench-tested the motor while the engine was out and it works just fine. So maybe it was wired wrong from the P.O.?)
So, either I really mislabeled something or it was already mis-wired previously. This Bus is pretty original, and I can't recall any examples of P.O. wiring hacks. Regardless, I'd appreciate being pointed in the right direction here, thanks. _________________ 1965 Beetle
1972 Westfalia |
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busdaddy Samba Member

Joined: February 12, 2004 Posts: 52574 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Tue May 06, 2025 4:19 pm Post subject: Re: Need VR/Alt wiring help '72 |
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The one you are calling green looks blue from here to me, the blue/yellow is an odd combo for that circuit but VW has subbed wire colors in the past if they were low on the correct stuff.
That blue wire from your new harness connects to the blue (or green?) wires that go into the connector with the blue tape on it. _________________ Rust NEVER sleeps and stock never goes out of style.
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BruceJ Samba Member
Joined: June 16, 2009 Posts: 260 Location: Portland, ME
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Posted: Wed May 07, 2025 5:14 am Post subject: Re: Need VR/Alt wiring help '72 |
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busdaddy wrote: |
The one you are calling green looks blue from here to me, the blue/yellow is an odd combo for that circuit but VW has subbed wire colors in the past if they were low on the correct stuff.
That blue wire from your new harness connects to the blue (or green?) wires that go into the connector with the blue tape on it. |
Okay, that makes sense, thanks. But what to do with that black wire? Going by standard VW wiring conventions black would mean switched hot, but I have no idea what this would power. Wishing I'd done a better job photographing/labeling before I took everything apart. _________________ 1965 Beetle
1972 Westfalia |
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busdaddy Samba Member

Joined: February 12, 2004 Posts: 52574 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Wed May 07, 2025 7:22 am Post subject: Re: Need VR/Alt wiring help '72 |
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BruceJ wrote: |
...... Going by standard VW wiring conventions black would mean switched hot,.......... |
Correct, but in this rare exception it's test network terminal #14, tape it up. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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BruceJ Samba Member
Joined: June 16, 2009 Posts: 260 Location: Portland, ME
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Posted: Wed May 07, 2025 8:17 am Post subject: Re: Need VR/Alt wiring help '72 |
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busdaddy wrote: |
BruceJ wrote: |
...... Going by standard VW wiring conventions black would mean switched hot,.......... |
Correct, but in this rare exception it's test network terminal #14, tape it up. |
Ah, the orange spot #14 on the diagram, with the connector for the black wire that would've originally led up to the alternator harness. Though I do wonder where the other end of this black wire goes after it disappears into the harness forward, I'll go ahead and tape it up.
Thanks for clarifying things, BD.  _________________ 1965 Beetle
1972 Westfalia |
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telford dorr Samba Member

Joined: March 11, 2009 Posts: 3623 Location: San Diego (Encinitas)
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Posted: Wed May 07, 2025 8:31 am Post subject: Re: Need VR/Alt wiring help '72 |
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Is the GEN dash light behaving properly? If so, it's wired correctly. The blue alternator wire goes to the GEN dash indicator. Normally, the mating body harness wire is a single wire. _________________ '71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST) |
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BruceJ Samba Member
Joined: June 16, 2009 Posts: 260 Location: Portland, ME
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Posted: Wed May 07, 2025 9:00 am Post subject: Re: Need VR/Alt wiring help '72 |
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telford dorr wrote: |
Is the GEN dash light behaving properly? If so, it's wired correctly. The blue alternator wire goes to the GEN dash indicator. Normally, the mating body harness wire is a single wire. |
Yes, it was before I pulled the engine, and the alternator was charging just fine. And I thought the same, one blue wire to one blue wire, although my Bentley clearly shows (now that I've studied it) a Y-connector with second wire going up to the blower relay.
I'm thinking that I'll wire it up as BD suggests. The first test will be if I get the GEN light when I turn the key ON (not start). If no light (along with the oil light and, if I recall, brake warning) then I have some further sleuthing to do. Sound about right? _________________ 1965 Beetle
1972 Westfalia |
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Bnanwel Samba Member
Joined: November 10, 2022 Posts: 249 Location: Ft Lauderdale
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Posted: Wed May 07, 2025 9:43 am Post subject: Re: Need VR/Alt wiring help '72 |
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Are you sure that “black” wire is black. Peel back the sheath near the grommet and expose some clean wire insulation to confirm it’s not just oily scum hiding the actual color. _________________ ‘72 Karmann Ghia Conv.
‘73 Karmann Ghia Coupe
‘74 Karmann Ghia Coupe
‘70 Deluxe
‘72 Deluxe |
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BruceJ Samba Member
Joined: June 16, 2009 Posts: 260 Location: Portland, ME
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Posted: Thu May 08, 2025 11:03 am Post subject: Re: Need VR/Alt wiring help '72 |
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Okay, I rewired a few things, fired it up today and all is well! GEN light does what it's 'sposed to, and charging system seems fine.
While I was reaching in to re-do the wiring on this, suddenly I realized that a quick (and now obvious) test was staring at me right in my face--the network terminal, which I'd pretty much ignored until today. So I clipped one end of my VOM to the black wire by the firewall, stuck the other probe into where a black wire goes into the terminal, and whaddya know, continuity! I guess it threw me off that while the black wire -looks- like it goes up front, it actually doubles back and goes up to the terminal #14 (as has been suggested).
So, all good I think. . . .thanks for setting me straight! _________________ 1965 Beetle
1972 Westfalia |
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