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Dashboard Light

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by taz8000, Feb 1, 2001.

  1. taz8000

    taz8000 Guest

    There is a fibre optic cable dangling down from the back of my dash, this is connected to a lightbulb and emits light. Where does the other site fit to ???
    '87 Blazer 5.0 from Belgium
     
  2. bking

    bking 1/2 ton status

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    Fibre optic?
    I do know that on my 85 K5, there is a tiny TINY bulb that sits in the top of the ashtray in the middle of the dash, is that what you're talking about? What year is your Blazer?
     
  3. bking

    bking 1/2 ton status

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    Oops, sorry, it's an 87, ok, it might be the ashtray light, but, I don't understand what you mean by where does the other end connect to? Elaborate on your question.
     
  4. taz8000

    taz8000 Guest

    87 K5.
    The cable hanging down coms from behind the speedo, and the end lights up.
     
  5. taz8000

    taz8000 Guest

    Well I just don't know where it connects to as it is hanging down from the banck of the dash.
     
  6. bking

    bking 1/2 ton status

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    If it looks like a fibre optic light it must be the ashtray light..Open your ashtray and in the top left of the opening there should be a tiny light, if not then I bet thats where it goes. The bulb is sooooo tiny it looks like a fibre optic light, check and see. It has to clip in, in the top left of the ashtray opening.
     
  7. HarryH3

    HarryH3 1 ton status Author

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    Fuzzy memory here... I think that's part of the Vehicle Speed Sensor (VSS) circuit. Some years used a mechanical speedometer, then used pulsed light from a moving mirror inside the speedo head to signal vehicle speed to the engine management computer. There's a small plastic box under the dash that's called the VSS Buffer. One end of the fiber goes to the speedo, the other end goes to the VSS buffer.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    The VSS is held to the back of the speedometer by a VERY tiny screw, thus, it has a flat section that the screw head holds onto the speedo. the wires going to it, will as Harry said, feed to a yellow box, which is the buffer. The ashtray light, AFAIK, IS a fiber optic light, as it has no way to ground. (it mounts in plastic at the ash tray) That feeds off the back of the gauge cluster, off of the passenger side of the printed circuit board. It's not a very long cable/wire. The VSS IS longer, and reads the speedo cable revolutions via a reflective strip on the cable.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>
     
  9. bking

    bking 1/2 ton status

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    So, does that mean his Speedo won't work (because the light is hanging down?) IF it is working, then it's the ashtray light?
     
  10. bking

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    So, does that mean his Speedo won't work (because the light is hanging down?) IF it is working, then it's the ashtray light?
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    No, the speedo will work. The speedo, (not all I just found out, dad found a '91 Suburban with electric speedo) is mechanical. It is driven by the transfercase, basically. The VSS (Vehicle Speed Sensor) tells the TCC (torque converter clutch) by speedometer cable RPM that "I am above X MPH. Please lock up now" and thus, the TCC locks the torque converter. Thats overly simplified, there are more inputs, but that is what the VSS does. Either wire (VSS or ashtray light) can be unplugged and the vehicle will run. To the best of my knowledge the ash tray "light" has NO provisions for a bolt to hold it down. It is a press fit on one side, and somehow (crimped?) to a special socket on one of the gauge lights. That should help to ID. You will get to a small plastic yellow box if you trace the VSS wire.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>
     
  12. Sax Art

    Sax Art Registered Member

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    look at it this way......
    If you hook it up wrong, you can open your ashtray to check your speed, and flip your ashes in what used to be your speedometer!
     

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