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Tach and Coil question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 90idahoblazer, Aug 21, 2001.

  1. 90idahoblazer

    90idahoblazer 1/2 ton status

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    My 90 blazer had an after market tach on it and come to fine out ..it reads 500RPM high.....double checked it with 2 dwell/tach meters....all this time I have been chasing a gost on why its idleing high....If I were to remove it....which I am....where does that wire off the coil connect to.....does it just hang there? Because I know my rig didnt come with a factory tach....What is a good reliable tach i can buy thats not going to break into my life savings....thanks
     
  2. coloradoblazers

    coloradoblazers 1/2 ton status Premium Member

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    I installed a sun tach on my first car, and then on my blazer when i got it. So far it is great, just have to make sure there is no interfearence from the ground wire. Since it is aftermarket, shouldn't be hard to find the wire. Trace it back from the tack or remove the air cleaner and find the only wire coming off the coil that doesnt look stock. You can test it by sticking another tac in the sending unit and seeing if it reads. INstalling mine was mainly trial and error. Don't know if that helps, I have a 87 305 tbi. Shouldn't be too much difference. If all that get a chiltons or haynes repair manual and they will have everything you need w/ pics & diagrams.

    K-5- because size DOES matter!
     
  3. newyorkin

    newyorkin 1 ton status

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    The wire should just hang out (insulated, though) if you remove the AM tach. If you're going to put a new one in, though, I'd just chop off the wiring you're removing at the tach itself, and use wire the new one right in. A tach only needs a hot (power), ground, and tach (actual "input" from coil). Most also have a light, which wires into you're instrument lights. Pretty straightforward easy stuff. Like coloradoblazers said, trial and error shouldn't hurt you too much...[​IMG]
    I'm glad I saw this post, I wonder if this is why my Heep seems to be idling high...

    Good luck!

    Ratch
    <a target="_blank" href=http://k5.8m.com>k5.8m.com</a>
    **Ever stop to think... Then forget to start again?**
     
  4. scrapmetal

    scrapmetal 1/2 ton status

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    If it isnt a factory tach the wire will go to the fan side of the coil, the hot wire to the coil is the firewall wire, and the middle is a ground, on most Gm rigs there is usually a slot to hook the light hot wire into the fuse block, then ground the wire to the dash, then the other wire goes to the fan side of the coil, or if you go with a MSD, ignition you can just hook up the tach wire to the side of the MSD unit, but I would imagine if its isnt a factory tach wire that it may be not grounded properly or the wrong wire all together, sometimes the alternators will send or interupt the signal to the tach itself,, or maybe not, its hard to diagnose it not being able to see it, by the way, Im Idaho too, northern

    Never been stuck, just temporarily delayed.
    <a target="_blank" href=http://hometown.aol.com/bcscrapper/myhomepage/index.html>hometown.aol.com/bcscrapper/myhomepage/index.html</a>
     
  5. 90idahoblazer

    90idahoblazer 1/2 ton status

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    thanks guys......
     

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