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  1. #1
    Member
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    Tach challenge

    Looking for some help. I have a 1970 911 that I installed a 3.0, now the tach doesn't work. The shop told me to install a SC tach. I don't want to install it wrong.

    The original tach went from left to right blue wire yellow stripe, black and purple and the brown was a ground. Do I hook it up the same way with the SC tach?

    Thanks
    Don
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  2. #2
    Just look at the symbols on the spade connectors. Blue/yellow is power and goes to the + terminal (or it may be marked 12V) Black/purple goes to terminal TD, and brown is always ground and goes to terminal marked with a -
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  3. #3
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    Yes Ed power on blue yellow. Connected it that way turned key on tach went to 6 grand with out running.

  4. #4
    The problem is not the tach but, rather, the tach signal. The early ignition (3-pin CDI) is a TD signal. The later SC ignition (6-pin box) is a different tach signal.

    Have your original tach converted or use the SC tach.
    -Marco
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  5. #5
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    Put in a SC tach because the original tach did not move

  6. #6
    But the problem is still the signal to the tach. Contact Bob Ashlock at Ashlock tech. He makes an adapter that should work for you.
    Early S Registry member #90
    R Gruppe member #138
    Fort Worth Tx.

  7. #7
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    Thanks Ed, I called Bob nice guy, I need to check engine harness to CDI box to see if TD wire is connected. I ordered the adapter, rather use original tach anyway.

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