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02-17-2005, 04:54 PM
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#1 |
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Custer had a plan too.
Join Date: Dec 2003
Location: No. California
Posts: 344
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Tach Wiring
I will be installing a tach dash in place of my idiot light dash.
When I hook up my diagnostic tach, I clip to the hei "tach" connector and to a ground. Why does a factory tach need 12v?
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72 K15 GMC (aka Big White) Performance Rockers, Cab Corners, and Floors Fossil Fuel Glutton Neighborhood Nuisance 98 BMW 540i for Speed (Sold  )05 Subaru Outback for mileage |
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02-17-2005, 06:29 PM
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#2 |
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Registered User
Join Date: May 2000
Location: Petrolia,Ontario,Canada but working in Port Huron,Mi.
Posts: 1,772
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Yes,Tach signal and 12v+ are the only connections on the back of the factory tach.
I believe the tach is grounded through the inst. cluster.
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71 blazer,350SBC,approx.375HP,700R4,factory GM TPI.Dual electric fans,33x12.5x15 ATR on stock suspension. Petrolia,Ontario,Canada but working in Port Huron,MI. See ALL my Blazer pic's HERE |
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02-17-2005, 07:39 PM
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#3 |
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Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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avejoe,
Most diagnostic tachs are battery powered with small replaceable batteries or some internal power source so they do not need power, just the signal and ground. Factory tachs are powered off of the vehicle's 12 volt battery source since they are not set up with a separate battery and they require more power than the diagnostic tachs.  Jim |
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02-17-2005, 07:45 PM
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#4 |
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Registered User
Join Date: Nov 2000
Location: Huntsville Ontario Canada
Posts: 4,051
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Hey Jim How would I hook up My stock Tach to my HEI ?
Thanks, MArio
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1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD |
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02-17-2005, 07:56 PM
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#5 |
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Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Hooking up a stock tach to an HEI is pretty straight forward. Plug the 12 volt wire onto the "ignition unfused" terminal on the fuse panel and plug the wire from the tach terminal marked "coil" into the HEI terminal marked "Tach".
The tach will get its ground from the metal part of the gauge package. You will need the right ends on the wires and it is a good idea to install a small in line fuse on the power wire. If you don't have the right ends or need a picture of them, let know. Jim |
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02-18-2005, 12:25 AM
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#6 |
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Registered User
Join Date: Nov 2000
Location: Huntsville Ontario Canada
Posts: 4,051
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Thanks
I can get all the correct plugs at a shop in town here I just was confused on how to wire it up. It's pretty easy I guess.
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1968 Suburban numbers matching all original truck now equipped with 6.0/4L80 on Accuair http://67-72chevytrucks.com/vboard/s...d.php?t=625017 1967 C/20 6.0/4L80 Roofing Truck 1990 V2500 Suburban "Plow Truck" 2005 TAHOE DD |
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02-18-2005, 02:30 AM
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#7 |
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Custer had a plan too.
Join Date: Dec 2003
Location: No. California
Posts: 344
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Thanks!
__________________
72 K15 GMC (aka Big White) Performance Rockers, Cab Corners, and Floors Fossil Fuel Glutton Neighborhood Nuisance 98 BMW 540i for Speed (Sold )05 Subaru Outback for mileage |
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