01-17-2019, 06:10 PM | #1 |
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Join Date: Aug 2012
Location: Central Illinois
Posts: 103
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Tach Project
I'm in the process of installing a tach from a larger GMC truck in a '65 C10. I've pretty well got the installation figured out, but the wiring has me a little confused. Most every tach I've encountered has two wires for the tach to function. 12 volt power and another that goes to the - terminal on the distributor or tach terminal on HEI.
This tach is secured in the can by 3 studs with only 1 stud being insulated from the case and no spade terminals for the wires. The case is stamped AC Div. GMC. I know the tach came out 0f a '70s-''80s big GMC gas burner. Anyone know anything about this style tach? Any help appreciated! Just looked at the tach and found a date October 13,1977 Last edited by spudder; 01-17-2019 at 06:16 PM. Reason: More Information |
01-17-2019, 07:24 PM | #2 |
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Location: China Spring, TX
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Re: Tach Project
Oh ya, that's your basic 12-2 Alpha-Delta Charlie right there. Yep.
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01-17-2019, 07:30 PM | #3 |
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Location: Sherman, ME
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Re: Tach Project
I haven't seen one exactly like that before, but GM did have some tachometers that used a simple 1-wire hookup to the negative side of the coil (no connection to 12v power).
Here's a link to an old GM tachometer service bulletin --> http://www.oldsmobility.com/img/pdf/...air_Manual.pdf See the non-transistorized "Group 1 inductor type" tachometers as described on pages 12 through 14. The internal schematic is shown in figure 8 on page 27. |
01-17-2019, 07:31 PM | #4 |
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Join Date: Feb 2016
Location: Georgetown, TX and Bragg Creek, AB
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Re: Tach Project
Spudder,
I have used a similar style tach in the past. I believe that the insulated terminal goes to the negative side of the coil/distributor and one of the two case studs goes to ground. (Doesn't matter which one) No 12 Volt power required. |
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