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BruceJ
Samba Member
Joined: June 16, 2009
Posts: 236
Location: Portland, ME
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 Posted: Tue Jun 15, 2021 4:16 pm Post subject: Brown wire alternator to regulator |
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Asking for a friend (really) . . .
'74 Bus, stock (?).
1. What is the function of the brown wire from the alternator to the regulator? Assuming it's a ground, but for what?
2. If this wire were fried, what would be the consequences, ie, would the engine run?
I do have the Bentley but those later wiring diagrams are a mystery to me.
Thanks.
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1965 Beetle
1972 Westfalia |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51124
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Tue Jun 15, 2021 4:22 pm Post subject: Re: Brown wire alternator to regulator |
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Yes, it is a ground, tell your friend it likely fried because the main ground strap at the nose of the transmission lost contact and all that starter amperage went looking for another path. That wire guarantees accurate voltage sensing for the regulator, it should still run without it, but the alternator may produce some funny volts, other systems like the FI might not like that.
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Rust NEVER sleeps and stock never goes out of style.
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Слава Україні! |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50337
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| Posted: Tue Jun 15, 2021 8:46 pm Post subject: Re: Brown wire alternator to regulator |
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| The brown D- wire carries the field current. It is grounded at its regulator end, but not at the alternator end according to the schematic, so if it is not passing current you would have no alternator output. |
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BruceJ
Samba Member
Joined: June 16, 2009
Posts: 236
Location: Portland, ME
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| Posted: Wed Jun 16, 2021 4:56 am Post subject: Re: Brown wire alternator to regulator |
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| busdaddy wrote: |
| Yes, it is a ground, tell your friend it likely fried because the main ground strap at the nose of the transmission lost contact and all that starter amperage went looking for another path. That wire guarantees accurate voltage sensing for the regulator, it should still run without it, but the alternator may produce some funny volts, other systems like the FI might not like that. |
Ok, makes sense, and serves as a reminder that we should double-check the grounding strap.
Might the fact that the brown wire is toast mean that the voltage regulator could have been damaged as a result (assuming it was working fine before)? Thinking about whether I should have a replacement on hand when he and I have another go at getting the thing started.
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1965 Beetle
1972 Westfalia |
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BruceJ
Samba Member
Joined: June 16, 2009
Posts: 236
Location: Portland, ME
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| Posted: Mon Jul 19, 2021 12:54 pm Post subject: Re: Brown wire alternator to regulator |
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Cleaned up both ground straps and replaced alternator harness. Started right up, thanks!
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1972 Westfalia |
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