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Thread: 1988 gmc speedometer

  1. #1
    Join Date
    Jul 2009
    Posts
    1

    Default 1988 gmc speedometer

    I just purchased an 88 gmc 1500 for my son. the speedo was working but quit. We replaced the auto tranny sender and it still isn't working. I put it on a lift and checked it in gear and it s not getting power to the sender. the fuse is good. What next?

  2. #2
    Join Date
    Jan 2007
    Posts
    4,850

    Default

    Hi kingkeith27,

    The VSS is a permanent magnet generator that sends an AC voltage signal to the instrument cluster. It creates 40 voltage pulses for every revolution of the transmission output shaft; solid state circuitry within the instrument cluster interprets these pulses and control the speedometer and odometer.

    Diagnosing the system can be kind of involved. Email one of our tech service reps at research@haynes.com. Give them the number of the Haynes manual you're using, and the number/letter combination on the title page, just to the right of the Haynes logo - it looks something like this: (2X3 - 38010). They'll do what they can to help.

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