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What is this 4th wire on Alternator?

Discussion in 'Technical Discussion' started by Capt GG, Apr 21, 2023.

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  1. Capt GG

    Capt GG New Member

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    Sep 20, 2021
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    Washington, NC
    I'm replacing a Volvo Penta TAMD74EDC 24v alternator and when I received a "compatible" replacement, it is missing a 4th wire which comes out of the regulator. The photo is my existing alternator; the D+ and B+ wires have already been removed. I'm assuming the small gauge red wire coming out of the regulator is voltage monitor to my helm monitor/light. Can anyone confirm? If so, can I just place this wire on the B+ terminal?

    Attached Files:

  2. Capt Ralph

    Capt Ralph Senior Member

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    With such little information, alternator model numbers (in & out), no schematic or ships install diagrams,, it will be hard for anybody to answer this question,
    except maybe from the guy that sold you the "compatible" replacement.

    Your experimenting with electricity and expensive equipment and no DIY warranties.
    I hope you have good luck.
  3. Capt GG

    Capt GG New Member

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    The existing alternator model number is provided (Valeo H642509A) and if I was experimenting, I'd just install the replacement and cross my fingers, which I won't do. I have no schematic/ships diagram, or I wouldn't be here reaching out in the hope of constructive comments. Valeo has no cross reference for this model. As for the "replacement", the model number is irrelevant. I've also reached out to Viking and Volvo. Further research tells me the small gauge red wire leading into the regulator is a remote sense from the battery-side of the isolators. I'm going to ping that out to confirm.
  4. Capt Ralph

    Capt Ralph Senior Member

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    IMG_7960.jpg
  5. Capt GG

    Capt GG New Member

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    I rest my case. Thank you for your comments.
  6. YachtForums

    YachtForums Administrator

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    Capt CG,

    Ralph is generally helpful but his humor might be hard to read. I know you cross posted to other forums in search of answers. We run a tight ship but sometimes any crew can become mutinous. Hopefully you will find more constructive guidance moving forward.
  7. Pascal

    Pascal Senior Member

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    I guess pointing out to the made in china label would be seen as non constructive :)
  8. jeduardo

    jeduardo New Member

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    Maybe it's a D+
  9. jeduardo

    jeduardo New Member

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    If you look inside the letter "o" you will see that the inner corners are square
  10. Sarnico

    Sarnico New Member

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    Capt CG, can't tell you what it is but it is normally connected to the B+ pole on the generator:

    [​IMG]