Underhood Ammeter Bypass

Electrical & Ignition

  1. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    As requested,A couple members,some experienced,some newbies,asked for me to do a detailed pictoral of adding the extra wire under the hood that will keep your car alive and save your sneakers for walking the dog.
    I done this soo many times I never really did any pics of it.
    Using Maggie's 69 Fury III "Frankie" as the demonstrator.
    Besides, I wanted to do this anyways since it was never done on this car.
     
    Last edited: May 23, 2020
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  2. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Step 1. Disconnect battery.
    Step 2. At the back of the alternator,run a 12 gauge or heavier wire starting at this 7/16" nut.
    20200523_115726.jpg
     
  3. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Run the wire the same way as the original harness.
    You can hide the wire or use wire looming but for this thread I left the wire exposed for clarity..
    20200523_121233.jpg
     
  4. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    The other end stops at starter relay.
    Depending on what year most are either on the firewall or left inner fender..
    20200523_121345.jpg
     
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  5. 69psf

    69psf New Member FCBO Gold Member

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    Great info - thanks for that!
     
  6. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    At the relay use a fusible link. I used an 18 gauge with my 12 gauge wire.
    Fury only has a 38 amp alternator.
    On my other car,I am running a 78 amp alternator and used 10 gauge wire with a 14 gauge fusible link.
    20200523_121314.jpg
     
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  7. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    I used male and female insulated spades for future repairs.
    Thus wat I can replace the fusible link and not cut into the wire.
    20200523_122204.jpg
    20200523_122825.jpg
     
    Last edited: May 23, 2020
  8. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Hook up the fusible link to the battery stud at starter relay. Some cars have 1/2 wrench or others need 9/16' for the nut..
    20200523_122837.jpg

    View attachment 378441
     
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  9. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Button up the relay tidy up the wires reconnect the battery and enjoy!
    Our guinea pig shown here from today..under construction,LOL

    20200523_115703.jpg
     
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  10. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    It took longer to do the thread compared to the wiring,LOL!!
    But I cannot stress enough how important this 15 minute job is .
    What it does is piggy back on the ammeter circuit. This wire takes 50% of the load away from the ammeter itself.
    We all know the ammeter gauge is the achilles heel in our beloved old Mopars.
    The fusible link is a safeguard should the alternator short out and not burn the dash or car to the ground.

    You wil notice that the ammeter gauge will not swing as crazy as before and will not read 100% accurately.
    But still works--until is does short out but the car will still function normally on a day to day basis.
    An option is install an afermarket volt gauge.
    Simpy hook it to a switched 12 volt source and ground it to body. done.

    In laymans terms the Red wire at starter relay goes through the bulkhead and eventually to the ammeter gauge--which is hot all the time.
    Hot I mean live as in anything that is run by battery no ignition key needed (headlights,hazards,dome light lighter,etc)
    The black wire on the ammeter goes to the ignition switch which as you know powers anything that needs the key on.
    So when the ammeter shorts out you have NOTHING!
    This simple little addition is worth its time,trust me.

    I cannot take credit for this mod.I first read about it in MOPAR ACTION
    20 years ago writen by Richard Ehrenberg.
    Hope this helps.
     
    Last edited: May 23, 2020
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  11. C Sickness

    C Sickness New Member

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    The ammeter is a gauge that measures current flow. The Needle responds because it's connected to a small auxiliary winding that senses current flow through the main conductor in the meter. The meter is manufactured as what one could describe as "shorted". the "in" and "out" terminals are connected together. As long as this continues, all is well.

    What would make you walk home is a failure. The main conductor in the ammeter burns "open", resulting in a circuit disconnect. Battery charging ceases, and power is lost to the ignition switch.

    People like to say a failed electrical item is "shorted", when, actually, it has "failed open".

    This mod provides a secondary, "back up" circuit. Should the ammeter fail open, power is still provided to the key switch through the additional circuit.

    Probably the most important function of my Fluke meter is to analyze suspect components.
    Who still has their designed resistance?
    Who is shorted?
    Who is open?
     
    Last edited: May 23, 2020
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  12. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Thanks.
    For the Newer members or the less electrically versed I did not get too technical.
    I kept it simple.
     
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  13. furious70

    furious70 Well-Known Member

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    It is important to emphasize that when you do this the ammeter no longer indicates correct charging since the new circuit is on the 'back side'. The ammeter just measures the direction of flow, which can be either way now and still have a fully functional system.
     
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  14. Turboomni

    Turboomni Old Man with a Hat

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    May I ask why a fusible link and could you just use a fuse? Thanks for this as I think even I could do this!
     
  15. The Captain

    The Captain Active Member

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    I have done this numerous times and the ammeter works but reads backwards.
     
  16. furious70

    furious70 Well-Known Member

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    On a car with no other electrical mods, most likely because the new charge circuit is path of least resistance. But if you start adding a big stereo, a fuel pump, etc - where you source power for those will influence which direction current flows.
     
  17. Ross Wooldridge

    Ross Wooldridge Senior Member FCBO Gold Member

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    @cbarge Nice write up! Thanks for that.

    For clarification - is the alternator connection for the new bypass wire the same for older round back style alternators? Is it obvious?

    Also, again, for clarification for those of us clueless about electrical - does one leave the original wire to that stud on the alternator (the black one with the red insulator in your first picture), or disconnect it and leave it dangling? When the nut goes back on the alternator with the new wire, will there be two wires (the new and the original), or JUST the new wire there?

    As well - how about detailing the "ammeter feed bulkhead bypass" procedure - like my Monaco had done at the factory as per the police wiring. We gotta get that big power OUT of the bulkhead spade connectors. That's the biggest fire starter there is.
     
    Last edited: May 23, 2020
  18. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    You can use an inline fuse for sure! No problem both work the same way in principle.
    I am used to using the fusible links that's all.
     
    Last edited: May 23, 2020
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  19. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Yes it is. You will have two wires at the stud of alternator '--original and new addition
     
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  20. cbarge

    cbarge World Famous Barge in a Budget FCBO Gold Member

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    Which why I recommended an aftermarket volt gauge for those who really like to keep tabs.
     
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