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  1. 01-02-2021, 07:22 AM #1
    tom1394racing
    tom1394racing is offline
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    Tach/Ballast Resistor Question

    I am about to do the first start and break-in run on the engine in my '70E project. I have spun the engine with the starter to ensure fuel and oil pressure and no leaks. I have also checked to ensure spark. However, the Tach shows no response when the engine spins on the starter. I would like to make sure the Tach works so that I can set the RPM at 2000 for the first 20 min break in run.

    I am not surprised that the Tach does not respond as it is wired through the ballast resistor but is a later model Tach that should not require the ballast resistor to condition the signal (see photo). From what I have researched, I should be able to make Tach signal from the coil bypass the ballast resistor by connecting the blue/yellow wire from the coil directly to the black/purple wire to the Tach. I plan to jump these two wires underneath the ballast resistor (see photo) and leave the ballast resistor in place for appearances.

    Is this the correct approach to make my existing Tach work?
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    Tom Butler
    1973 RSR Clone
    1970 911E
    914-6 GT Clone in Progress
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