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Thread: SEV Marchal Voltage regulator same (function) as Bosch voltage regulator?

  1. #1
    Registry member# 206 fourteenten's Avatar
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    SEV Marchal Voltage regulator same (function) as Bosch voltage regulator?

    Hi there,

    Is the SEV Marchal Voltage regulator as pictured the interchangeable (if it fits on the panel) with the Bosch voltage regulator? Am I right that you need a Bosch dizzy and alternator as well from the same brand to make it all work..

    Thanks,

    Cees
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    Last edited by fourteenten; 10-24-2020 at 03:47 PM.

  2. #2
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    If you follow the engine bay jamb stickers , the brands cannot be intermixed .

  3. #3
    Senior Member NorthernThrux's Avatar
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    Dizzy doesn’t matter, but matching alternator does. This is because the SEV Marchal alternator has 2 isolation diodes in parallel between it and the battery, while the Bosch does not. So you need a voltage regulator that has a 0.7V higher setpoint (1 diode voltage drop) to generate the same voltage at the battery than the Bosch unit. If you use a Bosch regulator, or most of the modern solid state replacements with your Marchal, your charging voltage will be 0.7V too low and eventually your battery will be discharged.

    Ravi
    Early 911S Registry # 2395
    1973 Porsche 911S in ivory white 5sp MT
    2015 Porsche Macan S in agate grey 7sp PDK

  4. #4
    Registry member# 206 fourteenten's Avatar
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    Thanks Ravi and Richy, it makes sense to find a replacement for the Marchal if it does not work.

    Cees

  5. #5
    Senior Member NorthernThrux's Avatar
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    This one works. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    I have thread somewhere on how you can make it look like your old VR to the casual glance.

    Ravi
    Early 911S Registry # 2395
    1973 Porsche 911S in ivory white 5sp MT
    2015 Porsche Macan S in agate grey 7sp PDK

  6. #6
    Will the Marchal VR work with the Bosch alternator? That is how my ‘70E project was configured before my restoration.
    Tom Butler
    1973 RSR Clone
    1970 911E Restoration in Progress

  7. #7
    Senior Member NorthernThrux's Avatar
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    It will, but it could lead to excessive electrolyte loss in your battery. You’ll be charging with 0.7V higher than you should be. I see 14.1V at fast idle right after startup. You’d see 14.8V. That’s too high for a lead acid battery and borderline for a AGM battery.
    Early 911S Registry # 2395
    1973 Porsche 911S in ivory white 5sp MT
    2015 Porsche Macan S in agate grey 7sp PDK

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    Quote Originally Posted by NorthernThrux View Post
    This one works. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    I have thread somewhere on how you can make it look like your old VR to the casual glance.

    Ravi
    Hi Ravi,
    can you please post a link?

  9. #9
    Senior Member NorthernThrux's Avatar
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    Quote Originally Posted by fizeus View Post
    Hi Ravi,
    can you please post a link?
    https://www.early911sregistry.org/fo...=1#post1067854


    BTW Tom, if you have an original SEV Marchal VR, thye are actually adjustable and you can solve that overvoltage charging issue. There is a thread on Pelican or here on how to adjust them.
    Early 911S Registry # 2395
    1973 Porsche 911S in ivory white 5sp MT
    2015 Porsche Macan S in agate grey 7sp PDK

  10. #10
    Ravi

    Thanks for your replies. I have dual Sonnenschein AGM’s in my 70 project. I have the same battery in my 73 hot rod and have been using it for several years now. The alternator in that car has an internal VR. I think I will check the charging voltage and then decide if I need to change out the VR in my 70 before I fire it up for the first time. I may go ahead and follow your lead on the solid state replacement transplant into an original Marchal case and have it ready in case I need it.
    Tom Butler
    1973 RSR Clone
    1970 911E Restoration in Progress

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