Underhood Ammeter Bypass

Electrical & Ignition

  1. furious70

    furious70 Senior Member

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    Depends on your expected system draw. The alternator won't produce more than the system draws
     
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  2. James Romano

    James Romano Well-Known Member

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    Yes and no. It provides a better path for the amps to flow. The last thing you want are your amps, from whatever source rating they are, passing through a rusty old bulkhead connector of questionable condition. Then on top of that...through a 50 or 60 year old gauge. This provides a direct path with new wire to provide a safer path for the current to flow.

    There are other things to do like change your gauges to all electronic voltage regulator and swapping the ammeter to a voltmeter.

    But this is the easiest. For 20 bucks worth of wire and maybe an hours work... Your 25k (or whatever it's work to you) is 80,% more safer
     
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  3. Ross Wooldridge

    Ross Wooldridge Senior Member FCBO Gold Member

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    8 or 10 AWG would be a minimum size for the main wires, and 12 AWG for the fusible link.
     
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  4. 3175375

    3175375 Senior Member

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    Wire is sized to protect itself.
    It must be able to carry 90 amps in this situation.
     
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  5. furious70

    furious70 Senior Member

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    You would need to advise him to take considerable additional steps to be consistent with your advise. I.e. chase your advice all the way around the car and not just that one wire.
     
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  6. rsh1966vip

    rsh1966vip New Member

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    Thanks for the picture details. I am going to have read this more than once.
    rsh1966vip
     
  7. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Any questions PM me.
     
  8. Gregg Benedict

    Gregg Benedict Member

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    I went to look for a Fusible Link for my bypass at the local Napa store. I thought that typical fusible links were short pieces of wire, typically about 6" or so. However, all I could get was this stuff. Will this work, by me just using a short piece and splicing it into the circuit?


    IMG_20211011_143237781.jpg
     
  9. Ross Wooldridge

    Ross Wooldridge Senior Member FCBO Gold Member

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    Yes. Cut to length and put your own ends on it. If the premade ones with the tags on them aren't available.
     
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  10. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    Depends.. Are you using #8 wire? If so, that is the correct size fusible wire.
     
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  11. Bucket

    Bucket Member

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    I'm guessing the underhood bypass would still be a good thing for my 1961 Newport which doesn't have a bulkhead connector ?
     
  12. Gregg Benedict

    Gregg Benedict Member

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    Yes... #8 wire for a 90 amp alternator...
     
  13. Trace 300 Hurst

    Trace 300 Hurst Professional Tinkerer FCBO Gold Member

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    And while you're at it, make two extra and keep them with the car.
     
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  14. Bucket

    Bucket Member

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    Trying to figure out how many amps my alternator is and what size wires and fusible links to use (or resettable circuit breaker ?)
    It has 2095191 on the front and has a twin pulley .
    I notice that cbarge says to use 12 gauge wire for a 38 amp alternator and 10 gauge for a 78 amp .
    Which would be the correct size wire for my alternator ?
    Cheers,
    Greg
     
  15. Knebel

    Knebel Senior Member

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    You wont hurt anything by going to a larger wire...
     
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  16. Bucket

    Bucket Member

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    Thanks for that.
    Does anyone know what size manual reset circuit breaker should be used with my alternator as described in my previous post .
    Spoke to the local auto parts shop (who are in the know) and they said auto fuesable wire is against ADR rules now .
     
  17. Mike66Chryslers

    Mike66Chryslers Senior Member

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    What are "ADR rules"? The only thing Google turned up was Alternative Dispute Resolution. Something to do with your insurance company?
    If fusible links are what your car came with originally, why would there be a problem retaining the OEM-style solution?
    You could also consider a MIDI/AMI fuse, AMG/MEGA fuse or similar high-current slow-blo strip fuse. MIDI are available in sizes up to 200A. If a circuit breaker is not "slow-blow", I would think a MIDI fuse sized to the max output of your alternator would be a better option. It could handle short durations of max output, but sustained max output would indicate a problem and the fuse would blow.
     
    Last edited: Nov 24, 2021
  18. Gerald Morris

    Gerald Morris Senior Member

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    Use a fusible link if its anything under 120 amps. SHIT ON what the auto parts liars tell you. They're just out to sell you crap, and they KNOW NOTHING! If you've got an alternator between 75 and 100 amps, and can keep your wire length under 6 feet, use #8 AWG, w 12 AWG fusible link wire, 6 inches, ideally between the battery + post and the charging lead from your alternator.
     
  19. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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  20. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    Does that rule apply to all the cars? There were millions of cars made by all the manufacturers with fuse wire. Or is it to any new wiring/construction?

    Looks like 50 amp for #10 wire.

    Choose_the_Fuse_Amperage.jpg
     
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