Am I hooking up my Tach wrong?
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Junior User
Joined: Feb 2004
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Am I hooking up my Tach wrong?
I cant seem to get my tachometer to work. I bought in in a junkyard. This is out of a 73 torino, to go in my 72 Ranchero. It only has 2 leads: Coil and Ign. It kept arcing when trying to hook it up. so I pulled it out and bench tested it (on top of the radiator, anyway): Positive went to the + battery terminal, and negative went to the negative post on the coil. Still arced! Now, a friend has a 78 Ranchero with a tach. We pulled it out and it has 3 leads, the add'l lead being a ground. Do the older tachs not use a ground? Grounded internally? Am I hooking this up incorrectly? Thanks
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Joined: Jan 2001
Posts: 56,992
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From: Virginia
Usually you have a hot wire and a ground or negative wire to power the circuitry in the tach, and then a trigger or pulse wire that hooks to the negative of the coil. On the aftermarket tachs, they usually have an additional wire for the dial illlumination.
