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brake light/cruise control switch question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sidepipes, Jan 24, 2003.

  1. Sidepipes

    Sidepipes 1/2 ton status

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    Maybe I'm stupid or something but isn't the switch supposed to have a normally open switch(brake lights) and a normally closed switch( for cruise control and TCC)?

    BTW, Its an 89 TBI, 700r4

    It seems both of my switches are normally open(so torque converter locks up with the brake pedal slightly depressed)

    Is my train of thought totally screwed up? or is there something wrong with the switch?

    Also there is another switch on the brake pedal with a vacuum line into it and a pink/black, and a blue/black wire attached( Don't offhand remember if its NO or NC). What is this for or is it a remnant from the 86 wiring harness?
     
  2. HarryH3

    HarryH3 1 ton status Author

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    I just went out and checked a brake light switch from an '88 I have in the garage. The two pins that go out the side of the switch close when pedal is pressed (switch plunger extends). The pair that goes straight out the back of the switch open when pedal is pressed.

    The one with the vacuum line is for the cruise control. At the same time it tells the cruise control electronics to turn off, it also vents the vacuum from the vacuum motor that pulls the throttle open. This way, even if the electronics screw up and don't turn off the cruise, the vacuum will get released anyway so that the throttle will return to idle, at least while your foot is on the brake. /forums/images/graemlins/cool.gif
     
  3. Sidepipes

    Sidepipes 1/2 ton status

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    Thanks, Harry.

    I'm gonna go pull the switch right now and go to GM tomorrow morning and get a new one.
    I'm pretty sure the switch I need is GM 25524845 or AC D850A.
     
  4. HarryH3

    HarryH3 1 ton status Author

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    /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     

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