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  • Speedo / Tach / Gauges: Tach stopped working

    64 GT Hawk and the tach stopped working. No movement at all.

    I have never messed with a tach and am pretty unfamiliar with how they hookup. Any suggestions on where to start.

    much appreciated.
    1964 Studebaker GT Hawk
    1970 Jaguar E-Type 2+2
    2003 Ferrari 575 Maranello (3 Pedal)
    2007 Jaguar XK Convertible
    2011 Jaguar XJL 5.0 SC

  • #2
    On the one hand, it did work for fifty-six years. OTOH, most failed far sooner. Solid state electronics were still in a pretty crude time of their development. Usually, it's the sending unit which fails.

    I've got a tach head and sending unit somewhere on the shelf which quit working and I never was able to find another sender to determine if the tach head was still functional.

    Anyone know of a bench test for the senders? Aren't there two versions? A round tuna-can shape and a rectangular brick?

    jack vines
    PackardV8

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    • #3
      I don't know about senders but for those tachs you can test with a C or D alkaline battery. If it moves to the left reverse the polarity and it should jump.
      Rob in PA.

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      • #4
        If I remember correctly, 62 to 64 Studebaker tachs need about 6 volts DC to make them register 6,000 rpm. I used my radio bench variable DC power supply to make the test several years ago when I had trouble with t he tach in my Avanti. The tach is a dc voltmeter so even a 1.5 volt flashlight battery should give an indication if the tach head is good. When the tach quit in my Avanti a few years ago, The failure was due to a bad integrated circuit in the sending unit and a 4 dollar part fixed that. Bud

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        • #5
          Of course...before beginning any testing on a vintage car...check all the connections for corrosion. It could merely be corrosion keeping it from completing the circuit.
          John Clary
          Greer, SC

          SDC member since 1975

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