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Technical Fuses - where are you using them?

Discussion in 'Traditional Hot Rods' started by cederholm, Jan 2, 2020.

  1. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    The "I" post goes to the coil side of the ballast resistor [to bypass it]. and only supplies power while cranking.
    The power feed should come off the "A" post via a fusible link [35a-40a]

    most cars take this feed off the starter solenoid post
     
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  2. cederholm
    Joined: May 6, 2006
    Posts: 1,619

    cederholm
    ALLIANCE MEMBER

    I like doing things the hard way.

     
  3. cederholm
    Joined: May 6, 2006
    Posts: 1,619

    cederholm
    ALLIANCE MEMBER

    Thats what I thought. So everything downstream of the fusible link is hot unless it passes through a switched relay.

     
  4. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    You're not actually.
    By getting a basic understanding of electrics ,it will get easier and easier .

    What I like about wiring is it is generally clean work [ diagnosing can be difficult]

    I remember years ago, looking at a tangled birds nest of wires . My mentor said "it is only the ends of the wires that are important"
     
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  5. anthony myrick
    Joined: Sep 4, 2009
    Posts: 5,079

    anthony myrick
    Member

    You are my hero.
    Post pics how ya set it up
    I like learning
     
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  6. cederholm
    Joined: May 6, 2006
    Posts: 1,619

    cederholm
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    Couldn't agree more. And I'm pretty good with basic electric, though I always like a more experienced eye reviewing things like this. ...and as you've stated I get tripped up on the math. :eek:

    Hi Anthony, I'll post the outcome in my build thread shown in my sig. Feel free to check out the progress so far.

     
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  7. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    Yes, that is correct.

    now if you want to complicate things [as racers always do when trying to chase symplicity]
    Run a separate "charge" wire from the Gen/Alt to the same post "A" and put a decent diode inline.

    If you run an inline battery disconnect switch, you can kill everything with the engine running [it won't back feed] and it cannot discharge even if the gen wire is shorted out.

    This would be legal for most sanctioned motorsports [and perfect for long term storage]
     
  8. cederholm
    Joined: May 6, 2006
    Posts: 1,619

    cederholm
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    Cool, that's because the diode will only allow the current to pass in on direction, right?!?

    Also, I would like the main fused box on the switched circuit from the dash switch. As I DON'T want to run all the power through that switch I plan to use a relay to energize the fusebox. I doubt those Bosh style relays should be used for that, any recommendations?

     
  9. Boneyard51
    Joined: Dec 10, 2017
    Posts: 3,547

    Boneyard51
    Member

    There are any number of relays available through Borg Warner brand, that will handle the amperage.






    Bones
     
  10. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    Correct! That diode comes in handy when working around the engine bay . It is a very common practice on race cars .
    Are you using a normal on/off switch or an ignition key switch?

    Most accessories like Headlights /Taillights/ Stoplights /Interior Lights/ and Clock are wired before the Key
    [you want these lights to still operate with the ignition off for roadside safety]
    Ignition/gauges/wipers /heater motor/ radio/ turn signals/ and horn are switched [the horn has its own relay]

    So you will need a split fuse box with 2 feeds ,so a decent switch wont need a relay
     
  11. pprather
    Joined: Jan 10, 2007
    Posts: 1,616

    pprather
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  12. cederholm
    Joined: May 6, 2006
    Posts: 1,619

    cederholm
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    I plan to use the original model A key switch. I guess you’re right about splitting the fuse box.

    Near info about the diode too!




    Sent from my iPhone using Tapatalk
     
  13. solidaxle
    Joined: Jan 6, 2011
    Posts: 431

    solidaxle
    Member
    from Upstate,NY

    I like to keep all the components separately fused that way lets say your horn wire shorts out, you still have brake lights ect. I also draw everything out first, then just follow your diagram.
    Here's a crude drawings showing breakers and fuses.
     

    Attached Files:

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  14. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    This is correct......
    What we were just discussing , was the power feeds to the fuse box then they go to separate fuses
    Some are switched feed and some have direct feed
     
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  15. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    If you go down the relay route.........AND if you have working door switches , you can use a couple of relays so that the switched fuse box will stay activated even after the ignition is switched off ,then switched off when the door is open. [this is only for accessories and NOT the ignition]

    I have this on my 57 for the sound system, because the Ignition switch doesn't have an accessory position.
    I can listen to the radio with the key off [saving the points] .
    When a door is opened ,it switches off [until the key is switched on again]
     
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  16. Frank Carey
    Joined: Oct 15, 2009
    Posts: 484

    Frank Carey
    Member

    FWIW: My headlight switch (possibly GM) has two 12V input terminals. One for headlights and another for dash and parking lights. The headlight supply is protected by a fusible link. The parking light supply is fused.
     
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  17. koolbeans
    Joined: Apr 12, 2015
    Posts: 427

    koolbeans

    I agree. Took the words outa my mouth. Back in '68 in my quad headlights I used airplane landing lights on high beam. 2 am on the pa turnpike as I was hauling ass to Virginia, they started going on and off. Resettable circuit breaker saved from having a fire. And it's lonely at 2am.

    Sent from my XT1710-02 using The H.A.M.B. mobile app
     
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  18. southcross2631
    Joined: Jan 20, 2013
    Posts: 3,349

    southcross2631
    Member

    Here's a small fuse panel you can use for your car. I used an in line fuse on my electric fuel pump and a 30 amp breaker. I would use breakers for your head lights.
    You can install a hidden Maxi fuse to protect the whole system and it makes a good anti theft device.
    Most car thieve DSCF3494.JPG DSCF3492.JPG s don't carry a Maxi fuse in their pocket.
     
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  19. cederholm
    Joined: May 6, 2006
    Posts: 1,619

    cederholm
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    Sorcery!!!

    Okay, so I've updated my schematic (attached and headlight switch arrived in the mail. Slightly A generic vintage-style unit with attached circuit breaker which is clearly meant to handle most of the lighting circuits, and in my case all the un-switched circuits.

    Couple of notes about my schematic;
    • I'm using a vintage starter button that is designed to work as a grounding switch - hence to Bosh style relay in that circuit.
    • I am using a relay for all the switched circuits - even though my load is small, I don't feel good running everything though a 90 year old switch
    • the lines running off the bottom of the page are going to the gauge pod - I have a simple schematic for that.
    One question, on my schematic, were is the best place to wire in my ampmeter? just downstream of the fusible ling?

    Though from all appreciated.
    Carl.
     

    Attached Files:

  20. Boneyard51
    Joined: Dec 10, 2017
    Posts: 3,547

    Boneyard51
    Member

    Depends on what you want your amp meter to show.








    Bones
     
  21. cederholm
    Joined: May 6, 2006
    Posts: 1,619

    cederholm
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    If the draw is coming from the generator or the battery.




    Sent from my iPhone using Tapatalk
     
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  22. solidaxle
    Joined: Jan 6, 2011
    Posts: 431

    solidaxle
    Member
    from Upstate,NY


    I was referring to his original question. The conversation morphed in to something else. If you look at the PDF drawing I originally posted it shows an overall main breaker then the fuse block is a split bus. The Coil, Fuel pump and Start relay control circuit are fed off the on/off switch on my column drop. (Attached fuse block) . What concerns me the wire that feeds the two breakers under the dash, it is unfused. It passes through the firewall with in a rubber grommet, to one side of the starter relay. If the grommet were to deteriorate or falls out that wire would short to the metal.
    Traditionally the wiring from the battery to one side of the start relay contact is not fused but I am planning to add a 200a fuse link.
    Fuse block.jpg 200amp fuse.jpg
     
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  23. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    Personally, I think that the relay to the fuse is not needed because old 6V switches can carry more current than 12V switches [depending on condition]

    But if you do use relays, then mount them in a proper plug blocks [attached]
    Door Relay Blocks.jpg
    This photo is from the door switch relays on my 57 [I can post a schematic if you're interested]

    Where you suggested for the Ammeter is where I would install it [you are trying to read if the Battery is charging or discharging]
     
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  24. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    I feel the pain ! I've had a 60's Austin Mini with the battery in the trunk do that and catch fire . A loose battery and Rotten grommets were the cause.

    HOT GLUE is your friend! Get a hot glue gun and squeeze glue around the grommets [and let it cool]
    When the glue cools it cannot chafe.

    Having spent years involved in racing, I have become a fan/believer in the Ford starter relay.
    It becomes a default fuse link that is normally switched off [until activated]

    If it was mounted 6" from the battery , the chances of a short between the Relay and Battery are highly unlikely.
    Then you would only need a fusible link [35a-40a] up to the fuse-boxes/Ignition switch.

    It would take a lot of energy to blow a 200a fuse [eg: starter cable shorting to the frame] but this would never happen if the cable was normally dead.
    It also makes a great automatic battery disconnect for storage

    It's just my opinion
    Maybe I've been hanging around race tracks too much
     
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  25. Ziggster
    Joined: Aug 27, 2018
    Posts: 577

    Ziggster
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  26. Boneyard51
    Joined: Dec 10, 2017
    Posts: 3,547

    Boneyard51
    Member

    Do not use the Ford starter relay! It is not a continuous duty relay and will fail, used like that! The Ford relay is designed to only be excited a short period of time to start the car. Left on continuously WILL burn it out and it will fail. Borg Warner and others make a universal relay that it continuous duty and can be triggered either through 12 volts or ground. I have used a bunch of them in my career.
    The Borg Warner number for the relay you need for this application is S-55.

    I also learned the car relays will fail the hard way!






    Bones
     
    Last edited: Jan 5, 2020
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  27. Mimilan
    Joined: Jun 13, 2019
    Posts: 379

    Mimilan
    Member

    Please read what I wrote again!
    It becomes a default fuse link that is normally switched off [until activated]

    You mount the relay next to a battery, and run the cable from the Ford Relay to the starter [If the starter is the solenoid type, the solenoid is also "Bridged]
    Between the battery and Ford Relay a wire [via fusible link] is run to the wiring harness [this is normally the same wire that comes off the starter solenoid]
    The wire from the starter button then goes to the Ford Relay. [the starter is already bridged]

    The Ford Relay only gets activated by the starter button, so the H/D cables are normally dead.

    This is a tried and true method to fix starter heat soak issues on Chevys. [check out post #26]

    On race cars [touring cars] they use a variation of this, because of the propensity for relocating the battery in the trunk or passenger compartment.
    There a 2 differences.[or 3]
    1: the power feed that goes to harness has a "Isolator/master switch" inline [this is positioned to be operated externally by track officials]
    2: The Alt/Gen goes directly back to the battery [or on the battery side of the "Isolator/Master switch"], This stops the charging system looping back to the ignition [ the whole system must kill a running engine when the Isolator/Master switch is off]
    Another advantage of this, is the charging system won't spike when the Isolator/Master is switch off, the charge still goes back to the battery
    [3:] a diode in placed in the charge wire close to the battery

    The downside to this is a couple of extra wires [starter button, charge] need to go back to the battery and relay

    Here is a rough schematic
    Wiring Schematic.JPG
     
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  28. Boneyard51
    Joined: Dec 10, 2017
    Posts: 3,547

    Boneyard51
    Member

    Ok , gotcha! That way the big starter wire( 0 or so) is not energized while racing, only while starting! That will work, just fine! I didn’t catch all that on the first read. I thought you were taking the ignition source down stream from the Ford relay. And it was staying on during the race. Your diagram made it clear as to how you are wiring your cars.

    I like that Ford product fixing that Chevy starting problem! Lol








    Bones
     
    Last edited: Jan 5, 2020
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  29. SquintBoy
    Joined: Mar 19, 2011
    Posts: 99

    SquintBoy
    Member

    Ms Mimilan, thank you for the schematic. It sounds like you really know this stuff! It was impossible for me to understand what these guys were talking about without pictures. You talked about road race cars having a few more wires. Would you please draw that schematic including the master cut off switch?

    Some questions:
    1. Any difference for generator cars?
    2. What size diode?
    3. What size or p/n fusible link?
    4. What size wire (other than the battery to starter cable)?

    Thanks for sharing your time and knowledge.

    Mark

    Sent from the red phone
     
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  30. donno
    Joined: Feb 28, 2015
    Posts: 400

    donno
    ALLIANCE MEMBER

    Remember, a fusible link does NOT blow like a fuse or trip like a circuit breaker. It MELTS!!
     
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