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markdtn · 08-05-2025, 01:20 PM

I have a Delco 10Si alternator hooked up as a 3-wire. So I am powering it with 12V to the tach. But the coil is 6V when running and 12V when starting using a 4-pole starter relay like many Fords with coils. I think if I am hearing correctly that I must use a 12V coil and get rid of the ballast resistor to make this work? If this is true, then modern tachs don't work on Fords or GM into the mid 1970s? (Pre Duraspark and HEI)

What is the latest and greatest on a good 12V coil? Bosch blue 00012?

08-05-2025, 01:20 PM	#10
markdtn Senior Member Join Date: Jun 2016 Location: Chattanooga, TN Posts: 164	Re: Modern Tach won't work with points? I have a Delco 10Si alternator hooked up as a 3-wire. So I am powering it with 12V to the tach. But the coil is 6V when running and 12V when starting using a 4-pole starter relay like many Fords with coils. I think if I am hearing correctly that I must use a 12V coil and get rid of the ballast resistor to make this work? If this is true, then modern tachs don't work on Fords or GM into the mid 1970s? (Pre Duraspark and HEI) What is the latest and greatest on a good 12V coil? Bosch blue 00012?