MSD Ignition Box, Tach wiring? |
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MSD Ignition Box, Tach wiring? |
dbledsoe |
Sep 26 2005, 01:58 PM
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#1
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Mutineer Group: Members Posts: 300 Joined: 13-May 03 From: Boise, ID. Member No.: 687 |
I'm nearing the final stages of a Buick V6 swap into my 914. I am using an MSD billet distributor and MSD 6200A ignition box. As best I can tell from the Haines wiring diagram, the 914 12 pin harness wire, black wire with purple stripe that normally connects to the negative side of the coil, is the tach signal wire. I am guessing (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif) that the black/purple wire would be the one to connect to the MSD box tach output signal connection. Can anyone correct me on this if I am wrong in my guess? (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif)
Thanks, Don |
lapuwali |
Oct 3 2005, 05:37 PM
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#2
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Not another one! Group: Benefactors Posts: 4,526 Joined: 1-March 04 From: San Mateo, CA Member No.: 1,743 |
The early and late tachs take different signals. I'm not sure the switch was exactly when they went from silver button to no-button. The late tachs are happy with a simple square wave of well under 12v (even 5v might work). The early tachs need the ringy, spikey (up to 30v) signal straight off a coil to work. The primary difference appears to be a single resistor inside the tach, the early ones having one to limit the spike currents, the later ones lacking this resistor. There are detailed photos on this site of the tach guts and exactly what you need to do to do the conversion.
Once this is done, no adapter box should be required, and the late style will still work straight off the coil (w/o a CDI box). |
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