BOO Switch (in cars)

Discussion in 'General Electronics Chat' started by OmarAlMansoori, Oct 21, 2014.

  1. OmarAlMansoori

    Thread Starter New Member

    Oct 13, 2014
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    Hello, I'm doing some research on how the BOO switch stops the driver from changing the car from Park to Drive (for example). Could anyone fill me in on the details, I'm having trouble finding something that explains what the switch exactly does and how it locks the (shifter?).
    I would find it extremely helpful if someone could post the circuit the BOO switch is included in, in an average car. Also please keep it simple, I'm not that experienced with circuits (or cars).
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    there is a hydraulic line from the brakes that allows you to shift out of park only when the brakes are applied.
     
  3. OmarAlMansoori

    Thread Starter New Member

    Oct 13, 2014
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    I know just about that much, I was hoping to get a circuit that explains how it works in better detail
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    its not a switch, its a hydraulic cylindeer that locks the shifter mechansm in park unless the brakes are pushed.
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    You are obviously not solving the problem according to his perception of the issue.
     
  6. Papabravo

    Expert

    Feb 24, 2006
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    This is an ongoing problem. I have been the recipient of modest amounts of opprobrium for the very same transgression. I think we must all resolve to do a better job of adjusting our perceptions to those of the original posters. If that is not possible then I guess we must suffer the slings and arrows of outrageous fortune.
     
  7. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Can you give an example of a car that does this? It is done in all cars I'm aware of with a solenoid in the transmission. The brake light switch is now both a normally open(NO) contact type switch in modern cars, working with the brake pedal, they haven't been tied to the hydraulics since the 1970's. The NO contacts are for the brake lights, when the brakes are applied the lights come on. When the car is in 'park' the same contacts send a signal to the transmission ECU to engage the shift solenoid.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Here is a GM example, as you can see it is also dependant on the Park brake not being set and the foot brake on.
    Max.
     
  9. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    There's no cylinder but it just a electric solenoid on the shifter the prevents the shifter from moving ... That why there is a button on the shifter to release it ...It's called a shift override ...
    Trust me I towed cars for a living and that's how it's done or you can remove the shifter cable..
     
  10. alfacliff

    Well-Known Member

    Dec 13, 2013
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    mazda and ford use hydraulic interlocks. not switches. you can tell since the shifter will not move till you step on the brake.
     
  11. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Don't know about Mazda, but no Ford I've ever changed a transmission in had any brake and transmission connection. https://www.google.com/search?q=for...la:en-US:official&client=firefox-a&channel=sb

    And hydraulic brake light switches went away shortly after power disc brakes came into wide spread use. Due to the higher line pressure needed for disc brakes. The hydraulic switches diaphragm couldn't take the higher pressure.
     
  12. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    Any time you want to show me on my 6 fords where that is please do ... Also I will gladly rip out the 5r55e tranny out and you can show me
     
    shortbus likes this.
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