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What is this?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 87GMC, Mar 16, 2006.

  1. 87GMC

    87GMC 1/2 ton status

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    Does anyone know what this is? It plugs into the gauge cluster near the speedo cable. It's on my 87 that had TBI.

    for sale.jpg
     
  2. sweetk30

    sweetk30 professional hooker Premium Member

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    vss=vehicle speed sensor.

    used for cruise control stuff.
     
  3. 87GMC

    87GMC 1/2 ton status

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    I don't have cruise. So can I just beat it with a hammer and throw it away?:D
     
  4. Blue85

    Blue85 Troll Premium Member

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    I think the TBI ECU needs to know vehicle speed. They got if from the speedometer through that little box up until about 1990.
     
  5. mouse

    mouse 1/2 ton status

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    Used with the TBI as well. DONT destroy it, I will pay you to ship it to me if you want to throw it away...
     
  6. 87GMC

    87GMC 1/2 ton status

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    I was just kidding about destroying it. I'm pulling the TBI out of my truck and there was a wire to this.
     
  7. HarryH3

    HarryH3 1 ton status Author

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    If you look closely, you'll see two clear LED-looking parts on it. One lights up and shines into the speedo housing. Inside the speedo is a rotating reflective part that reflects the light back to the 2nd LED-looking part, which is an optical sensor. Each time the sensor "sees" the light, it sends a pulse to the ECM so that it knows how fast the vehicle is moving.
     
  8. 87GMC

    87GMC 1/2 ton status

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    I planning on selling the TBI once I get the wiring out. Would they need this and my gauges to make the system work? How do people convert to TBI without changing the gauges?
     
  9. HarryH3

    HarryH3 1 ton status Author

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    It would make it somewhat easier for them, if they wanted to mess with swapping out the dash, but there are aftermarket VSS adapters available from places like Jags That Run, Howell, Painless Wiring, etc.
     
  10. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    Not to hijack but - They got the vehicle speed from the speedo?! What kind of ass-backwards logic was that?! :confused:
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    The gauges are essentially the same about '82-89, most trucks even if not CCC, TBI, or equipped with cruise that vintage had the speedo setup to hold the optical eye for the VSS. So the gauges should be easy for someone to get if they don't already have them (older trucks start dealing with the mech oil pressure/amp gauge issue) but it certainly would make a TBI package deal more attractive to some people. Just unplug it all if you don't need it, and throw it in...not like you'll be paying shipping. :)

    As to getting the speed from the speedo, is there a better way to do it? Electronic speedometers didn't arrive until 1990 for the trucks, and they probably could have run something at the t-case like the aftermarket stuff, but that's an additional component/potential leak point, and 3ft of wiring vs 10ft (guesstimate) is more cost effective.
     

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