Five years ago I modified my 1970 distributor from the original breaker-point ignition system to the drop-in Pertronix electronic system. Pertronix doesn't need the old ballast resistor to work, so they tell us to remove it. The car has run perfectly since then, without any points to play with. My problem was, my tach died as soon as I did that.

For 5 years I've been trying to learn what to do to make the tach work again. I knew it was getting a signal from someplace because during long trips it would slowly creep up to 8,000 rpm and stay there until I shut the ignition off.

Last week I read on another Z site that some owner replaced his old ballast resistor and his tach came back to life. On Thursday I had the Z at Vinny's for a list of stuff and asked him to pop a standard ballast resistor back into it. VIOLA! My tach now works again!

The Pertronix electric ignition system doesn't need the resistor in order to work, but the tach does. The Pertronix works perfectly with or without the resistor, so there's no harm in leaving it hooked up.

Frank

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1970 240Z

Ha!

Glad you found the solution...I was voting on a bad tach. The ol' ballast resistor isn't so bad after all apparently .

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

Thanks ~ you can't imagine how happy it makes me to be able to count revs again.

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1970 240Z

I think you just splice the 2 wires together that used to go to the resistor.

So, you think the resistor itself isn't important, but just serves as a "bridge" btwn the connectors on either side of it? I guess that's possible; all the resistor would do is lower the voltage btwn the distributor and the tach. I guess I could test that by holding a jumper wire across the resistor and seeing if the tach quit.....

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1970 240Z