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Thread: battery cut off switch

  1. #1
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    battery cut off switch

    Hi All,
    Happy Friday.
    I am in the process of laying out my wiring harnesses. I am running a 5.0 Gen 2 Coyote motor.
    This is kind of a weird question-I know what the battery cut off switch does.
    Is it really needed? Or do guys install them for a extra level of security when the car is parked somewhere?


    I've seen them under the dash, on the trans tunnel, behind the passenger seat, and on the back wall of the cockpit.


    Let me know what you think on this
    Thanks
    Martin

  2. #2

    Steve >> aka: GoDadGo
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    I installed the switch shown below in the transmission tunnel so I can kill the battery if I have any electrical issues....The key was just a security bonus (Feel Good For Me!) that may help with security, or not.

    https://www.westmarine.com/buy/sierr...58?recordNum=8

    Though I found similar looking switches at the local auto parts stores, the amperage ratings of those switches weren't even close to the Sierra Switch plus those others appeared to be rather cheaply made.

    Good Luck From The Dark-Dart Side!
    Last edited by GoDadGo; 01-25-2019 at 09:59 AM.

  3. #3
    On a roll Al_C's Avatar
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    I installed the FFR switch on mine. It's above the trans tunnel under the dash. For me, it was more about additional security than anything else. Lots of guys install these switches for racing purposes, but typically those are someplace where they can be easily accessed.
    Mk IV Roadster - #8650 - delivered 7-17-2015 - first start 7-28-2018 - first go-kart 10-13-2018 - licensed and on the road 9-9-19: body/paint completed 3-17-2020.
    Complete kit / 2015 Coyote / TKO600 / IRS / Wilwood brakes / Mid-Shift mod / Power Steering / Heater and Seat Heaters / RT turn signal / Breeze radiator shroud and mount

  4. #4
    Senior Member MPTech's Avatar
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    I have the same one as GoDadGo. Couple advantages: theft security, electrical emergency, long-term storage (avoid draining the battery).
    F5R #7446: MK4, 302, T5 midshift, 3.55 Posi IRS, 17" Halibrands
    Delivered 4/4/11, First start 9/29/12, Licensed 4/24/13, off to PAINT 2/15/14!! Wahoo!

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    Quote Originally Posted by MPTech View Post
    I have the same one as GoDadGo. Couple advantages: theft security, electrical emergency, long-term storage (avoid draining the battery).
    A lot of people have this switch, but then they add a "keep alive" bypass that keeps allows some power to bypass the cutoff switch for the clock, radio, and EFI. I went back and forth on adding this bypass and installed it originally. Then I decided I really wanted to kill all the power with the battery cutoff switch, so I took it out (actually just removed the fuse for now). I figured the EFI settings would not "go away", and I wanted to be able to use the switch to kill the power to work on the car.

  6. #6
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    I installed one for two reasons: Safety and security. Mostly for the safety front so that as I am working on the car and before I have all of the wiring tied up I can cut the power when not in use.
    Ryan
    33 Hot Rod
    350 SBC with TKO 500, 3 link rear

  7. #7

    Steve >> aka: GoDadGo
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    I've also got this switch:

    https://www.amazon.com/Philmore-Swit...+barrel+switch

    installed inline with the clutch safety switch circuit.

    The key is removed in both the On and Off positions.

  8. #8
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    May sound crazy, but I put a heavy duty disconnect on the main power and used the one supplied with the kit on the "keep alive memory" wire. I can kill the mail power, which will not let the engine crank or run and still have the power to the ecu. If I need, I can disconnect the ecu power with the second disconnect. I put the main power switch on the back of the trans tunnel and the ecu switch inside the cubby hole behind the passenger. I should be able to reach through the hole and access the switch, if needed. I hope the ecu disconnect, keeps a clean connection. I guess I can just bridge it, if it becomes an issue.
    20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.

  9. #9
    Senior Member BEAR-AvHistory's Avatar
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    Have GoDadGo's red key switch wired with a 5amp self resetting keep alive circuit located on the U-Joint cover. Easy to reach & pull the key when you leave the car. If I only had the Coyote would have not bothered with the keep alive circuit but my other system for phone, music, maps would lose its mind.

    Full electric kill to work on the car requires a battery cable removal.
    Last edited by BEAR-AvHistory; 01-25-2019 at 01:14 PM.
    Kevin
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    I love the smell of 100 octane in the morning.
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  10. #10
    Seasoned Citizen NAZ's Avatar
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    I only installed one as NHRA rules require it, otherwise I wouldn't have bothered. How many factory cars have you owned with a master switch? To me, it's just added expense and complexity. But many folks feel it's value added so use it or not -- your choice. It's not like you're going to void the FFR warranty if you leave it off.
    Dart Little M 406" SBC 800 HP N/A & 1,100 HP on nitrous, 2-spd Powerglide with trans brake, 6,000 RPM stall converter, narrowed Moser 88 3.90:1 spool with 35-spline gun-drilled axles & Torino bearings, custom parallel four-link, custom tube chassis & roll cage NHRA certified for 8.5-sec (only two FFR Hot Rods have this cert).

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  11. #11
    Senior Member Dave Howard's Avatar
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    I installed the same switch as others with my Gen 1 Coyote. Put the switch on the back wall between the seats. It was an easy run since my battery was under the trunk. I didn't bother with the stay alive circuit. I know....you lose any self tuning and learnjng. After 40,000 kilometers, the car runs great. My intention was to have 100% electrical shut off.
    MkIV #7854, Kit picked up September 2012, Coyote/BOSS 302 intake tuned at 488HP, TKO600, Center Force, Moser 8.8, driveshaft safety hoop, Stainless Header 4x1x4 headers, Gas-N-sidepipes, rad shroud, Wilwoods, NO PS/PB, heater/defroster, heated seats, wipers, Herb door panels, Dynamat Extreme sound/heat dampening, premium Rodtop top, Fast Freddie lexan wind screen, Nitto 555R, drop trunk battery, drop trunk storage,

  12. #12
    Senior Member Itchief's Avatar
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    Martin

    When I build the car I didn’t install a battery cut off switch my though was I don’t plan on racing so why would I need a cut off switch. To make a long story short one day the starter bendix got stuck and the only way I could stop the motor was to remove the negative battery terminal cable once I got back home.

    I added the cut off switch between the seats at the same time I replaced the starter

    Rick
    #8475 Complete Kit Delivered Nov 2014, started Nov 2015, Street Legal Apr 2016, Paint and Interior Completed Aug 2017, 390 BBF, March accessory kit, MSD Atomic EFI and Ready to run, TKO 500 with MidShift kit, hooker headers, 3 link, track lock with 3.55, sway bars, power steering, wipers, heater

  13. #13
    Senior Member CraigS's Avatar
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    I had the usual cutoff switch in the trunk for about 5 years. Used maybe 3 times. When I moved the battery to the front I did not install a switch. Mainly because I hadn't used it enough to bother. But also because as a lexus tech, w/ the ever increasing number of systems w/ memory, we had all started replacing batteries w/ the engine running so we didn't have to reset everything. From that I realized that the switch would not shut off a running engine. It's been 5 years w/o the switch and I have yet to miss it.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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  15. #14
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    Thank you to all
    After all the input and talking to a few local Roadster owners, I am going to pass on the batter cut off switch-I don't plan on racing it. I will do a few autocrosses.
    Thanks again for all the input fellas . Have a great week
    Martin

  16. #15
    David aka Ducky2009 Ducky2009's Avatar
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    There are a couple ways to wire the cutoff switch. One is to kill ALL power. If you plan to use on a daily basis, killing all power will kill you clock, radio memory if you have a radio, and your ECU. The ECU has a learning mode, making adjustments to engine tuning, and retaining settings. If you kill the power, the clock and radio will need reset constantly. The ECU will re-learn.

    If you plan to race, it may be required to have a cutoff switch, depending type of racing.
    MK4 Build #9035 Delivered 2/17/17, First Start & Go-Kart 6/2/17, Licensed 9/1/17
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  17. #16
    Member Dewey McBride's Avatar
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    I have a hidden switch linked to my clutch. If I flip it, it bypasses the wire that tells the ECU that the clutch is engaged, and it won't start. I also have a battery cut off in the trunk for long term storage.

  18. #17
    Senior Member GTBradley's Avatar
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    I wanted a spare key for the Hella battery cut-off switch and thought I would post it here in case someone else needs it:

    HELLA 706729011 Replacement Key for Battery Master Switch

    BF3A3903-6957-457A-9F39-1FD5C6C380F5.jpeg
    Attached Images Attached Images
    Last edited by GTBradley; 12-12-2019 at 07:57 PM.
    Bradley

    Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.

    The distance between "finished" and finished is literally infinite.

  19. #18
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    Does anyone know where to get a spare red key for the Hella switch. just in case you loose the original
    M

  20. #19
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    I think the Harbor Freight disconnect is the same, if you have to buy the whole switch.
    20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.

  21. #20
    Senior Member Avalanche325's Avatar
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    Summit Racing
    https://www.summitracing.com/parts/hla-706729011

    I keep a spare hidden in the car.

    I have one of these for my keys and disconnect. Got it at Home Depot.

    key.jpg
    Last edited by Avalanche325; 12-11-2019 at 12:36 PM.

  22. #21
    Papa's Avatar
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    Quote Originally Posted by magicmarto View Post
    Does anyone know where to get a spare red key for the Hella switch. just in case you loose the original
    M
    That's what GTBradley provided a link for in post #17.
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  23. #22
    Senior Member GTBradley's Avatar
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    I received the key tonight and can confirm it does work in the FFR supplied battery cutoff switch.
    Bradley

    Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.

    The distance between "finished" and finished is literally infinite.

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  25. #23
    Not a waxer Jeff Kleiner's Avatar
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    Quote Originally Posted by GTBradley View Post
    I wanted a spare key for the Hella battery cut-off switch and thought I would post it here in case someone else needs it:

    HELLA 706729011 Replacement Key for Battery Master Switch
    Or if you're cheap like me you can go for the 68 cent variety

    https://www.ebay.com/p/12010304377?i...BoCcMoQAvD_BwE

    Cheers,
    Jeff

  26. #24
    Papa's Avatar
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    Quote Originally Posted by Jeff Kleiner View Post
    Or if you're cheap like me you can go for the 68 cent variety

    https://www.ebay.com/p/12010304377?i...BoCcMoQAvD_BwE

    Cheers,
    Jeff
    Jeff, you may be "cheap", but you do good work.

    Dave
    My Build Thread: http://thefactoryfiveforum.com/showt...ter-Build-9754
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  27. #25
    Senior Member GTBradley's Avatar
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    Quote Originally Posted by Jeff Kleiner View Post
    Or if you're cheap like me you can go for the 68 cent variety

    Cheers,
    Jeff
    Jeff, your timing is impeccable.
    Bradley

    Build thread - Mk4, Coyote, IRS, Wilwood brakes, old-style soft top and accessories.

    The distance between "finished" and finished is literally infinite.

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