Electrical Battery Cutt off Switch

Discussion in 'Fox 5.0 Mustang Tech' started by RangerJoe, Mar 14, 2013.

  1. RangerJoe

    RangerJoe Advanced Member

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    I really want to run in the NMRA True Street this year, so I have to get a battery cut off switch so I can pass tech with my battery in the hatch. I have narrowed it down to the Moroso 74102 or the Taylor 1033. The Moroso is rated to 300 continous amps while the Taylor is rated for 100 continous amps, with a 180 max peak rating. I'm not really sure if 100 amps is too little. I know my fans pull 30-40, then the headlights are probably the next biggest culprit. But I am unsure of the rest of the electrical system. Will 100 amps cut it, or do I need the 300 amper?

    Thanks,
    Joe
     
    #1
  2. 84Ttop

    84Ttop They make new pistons every day, so why worry?
    SN Certified Technician Mod Dude

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    Morose in my opinion if they were my only choices. I prefer the flaming river stuff, and use it on my personal car.
     
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  3. jrichker

    jrichker StangNet's favorite TOOL
    SN Certified Technician Founding Member

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    For a battery cut off switch, see http://www.moroso.com/catalog/categorydisplay.asp?catcode=42225
    is the switch http://www.moroso.com/catalog/images/74102_inst.pdf is the installation instructions.
    Use the super duty switch and the following tech note to wire it and you will
    be good to go.

    Use the Moroso plan for the alternator wiring and you risk a fire. The 10 gauge wire they recommend is even less adequate that the stock Mustang wiring.

    There is a solution, but it will require about 40' of 18 gauge green wire.

    Wire the battery to the two 1/2" posts as shown in the diagram.

    The alternator requires a different approach. On the small alternator plug there is a green wire. It is the sense lead that turns the regulator on when the ignition switch is in the run position. Cut the green wire and solder the 40' of green wire between the two pieces. Use some heat shrink to cover the splices. See http://fordfuelinjection.com/?p=7 for some excellent help on soldering & using heat shrink tubing.

    Run the green wire back to the Moroso switch and cut off the excess wire. Try to run the green wire inside the car and protect it from getting cut or chaffed. Crimp a 18 gauge ring terminal (red is 18 gauge color code for the crimp on terminals) on each wire. Bolt one ring terminal to each of the 3/16" studs. Do not add the jumper between the 1/2" stud and the 3/16" stud as shown it the
    Moroso diagram.

    How it works:
    The green wire is the ignition on sense feed to the regulator. It supplies a turn on signal to the regulator when the ignition switch is in the Run position. Turn the Moroso switch to off, and the sense voltage goes away, the voltage regulator shuts off and the alternator quits making power.

    The fuse & wiring in the following diagram are for a 3G alternator. The stock alternator uses a dark green fuse link wire that connects to 2 black/orange wires. Always leave them connected to the starter solenoid even if you have a 3G alternator.

    [​IMG]

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring
    http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

    Ignition switch wiring
    http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

    Fuel, alternator, A/C and ignition wiring
    http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
    http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

    Vacuum diagram 89-93 Mustangs
    http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg


    Rear mounted battery ground wiring. Follow this plan and you will have zero
    ground problems.


    One 1 gauge or 1/0 gauge wire from battery negative post to a clean shiny spot
    on the chassis near the battery. Use a 5/16” bolt and bolt it down to make the
    rear ground. Use a 1 gauge or 1/0 gauge wire from the rear ground bolt to a clean
    shiny spot on the block.

    One 4 gauge wire from the block where you connected the battery ground wire to
    the chassis ground where the battery was mounted up front. Use a 5/16” bolt
    and bolt down the 4 gauge engine to chassis ground, make sure that it the metal
    around the bolt is clean & shiny. This is the alternator power ground.

    [​IMG]


    The computer has a dedicated power ground wire with a cylindrical quick connect
    (about 2 ½”long by 1” diameter. It comes out of the wiring harness near the
    ignition coil & starter solenoid (or relay). Be sure to bolt it to the chassis ground
    in the same place as you bolted the alternator power ground. This is an
    absolute don’t overlook it item for EFI cars

    Note: The quick disconnect may have fallen victim to damage or removal by
    a previous owner. However, it is still of utmost importance that the black/green
    wires have a high quality ground..

    Picture courtesy timewarped1972 [​IMG]

    Crimp or even better, solder the lugs on the all the wire. The local auto stereo
    shop will have them if the auto parts store doesn't. Use some heat shrink tubing
    to cover the lugs and make things look nice.
     
    #3
  4. RangerJoe

    RangerJoe Advanced Member

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    Already had ya bookmarked there JRichker.;)

    I guess my earlier reply didn't load. Summit had a typo on their website. The Taylor unit is actually rated to 180 continuous and 1000 interment, so that kinda defeats the original question.

    Joe
     
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