tach
tach
New User
Joined: Oct 2004
Posts: 23
Likes: 1
Typically any aftermarket tach will have four wires. Red is positive, black is ground, green goes to the negative side of the coil (-), and white goes to an instument cluster light. That way when you turn your lights on at night your tach will illuminate as well. 
Post Fiend
Joined: Jul 2003
Posts: 11,945
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From: Spokane, WA
Originally Posted by The Shadow
Typically any aftermarket tach will have four wires. Red is positive, black is ground, green goes to the negative side of the coil (-), and white goes to an instument cluster light.
Senior User
Joined: Nov 2004
Posts: 158
Likes: 0
From: Centennial
Hey jpa......installation is pretty simple. A buddy of mine who does car stereos installed my Auto Gauge tach in my '76 F-250 390. We ran green through the firewall to the negative terminal on the coil. Red went to a 12V source. White went to the parking lights wire for illumination (but this didn't work so try another cluster lighting wire if possible). And then black was ground. My only issue is when the black wire is grounded and the white wire is on the parking lights it grounds out the parking lights and turns them off. We're still figuring that one out.....so maybe my wiring is screwed up or try another wire to illuminate the tach. I love the tach though and its great having the rpm info. Good luck!
Nate
Nate
Junior User
Joined: Sep 2004
Posts: 93
Likes: 0
I had my old boss install mine, not sure what he did, but mine is located right up against the pillar on the dash ( there was a small crack in it, so I decided to cover it up ). It looks good, easy to read. Its a Sun Sport II btw.
Postmaster
Joined: Apr 2000
Posts: 2,838
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From: SD
Originally Posted by MineralStang
My only issue is when the black wire is grounded and the white wire is on the parking lights it grounds out the parking lights and turns them off. We're still figuring that one out.....
Marty
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Senior User
Joined: Nov 2004
Posts: 158
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From: Centennial
Great Marty....thats what it does. The tach works, but the light doesn't. Defective out of the box...that sucks. Bought it from summit too. I just may go without the light because its going to bee a pain in the rear to pull it out and send it back (if they would help me anyway). I guess I'll see.
Nate
Nate
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Joe Kucinski
Senior User
Joined: Sep 2005
Posts: 359
Likes: 1
From: Saint Paul, MN
Just like Shadow said, hook the white Tach wire to an instrument panel light wire. The dimmer switch will dim the Tach light as well. Use a test light. The dimmer switch will dim the test light when you found the right one.
Postmaster
Joined: Feb 2003
Posts: 4,043
Likes: 4
Originally Posted by ford390gashog
ice man no coil has a negative wire that grounds it to the body both posts on the coil are positive it will say tach test
Actually a coil has 4 electrical connections. Postive and negative for the primary coil. Spark plug and ground for the secondary. The secondary ground is the metal case of the coil.