Tachometer Input Problem

Discussion in 'Shop Talk' started by Oxankle, Nov 11, 2005.

  1. Oxankle

    Oxankle Well-Known Member

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    Forgive me for asking a question here when I could buy a $50 book and get my own answer, but my truck is hardly worth a $50 investment. (Gee, and I just reminded myself that I left the windows down.)

    Anyway, for a long time now my tach has acted up. First it would work almost all the time, then quit for a bit. Then it got so it worked a bit less and loafed a bit more. Now it is down to the point where it only shows up for work now and then. When it does work the readings are just where they should be for a given speed.

    This is a '91 Dodge Dakota with two wheel drive, V6 engine. Is the tach pick-up electrical, and if so, does anyone know where it is located? The speedometer and odometer work just fine.
    Ox
     
  2. Cabin Fever

    Cabin Fever Life NRA Member since 1976 Supporter

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    I'm pretty sure that the pick-up comes off the distributor....at least that's where it was on an old 1990 dodge spirit I had.
     

  3. Hip_Shot_Hanna

    Hip_Shot_Hanna Well-Known Member

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    the other favorite place is the Alternator , (counts the AC pulse )
    Easiest way to check is nip off the belt and start it up no tach its off the alternator ( dont forget to put the belt back on )
     
  4. twohawlks

    twohawlks Member

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    Without looking it up in the manual my guess would the signal is supplied by the computer
     
  5. agmantoo

    agmantoo agmantoo Supporter

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    The tach in that vehicle plugs into a printed circuit and the contacts often get corroded where the tach mates to the board.
     
  6. Oxankle

    Oxankle Well-Known Member

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    Arrrgh!!!!! The area where my experience and knowledge is most deficient!!!!! What's more, I will bet a ten dollar bill againt the hole in a donut that the wire from the tach is bundled so that I cannot trace it.

    ARRRRGH!!!!!
    Ox
     
  7. Oxankle

    Oxankle Well-Known Member

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    OK;
    I have the bundle of wires going to the computer located; basically there is a bank of connections 6 inches long.

    To clean the contacts I will have to pull that bundle of wires.

    If I pull the plug to the computer and then plug it back, what have I fouled up? Is it safe to unplug the bundle and then plug it right back in, or will I have screwed up some settings?
    Ox
     
  8. agmantoo

    agmantoo agmantoo Supporter

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    Ox, I referenced the contacts to the tach where it connects in the instrument panel area. The connector to the computer should have an anti oxidizing "grease" on it.
     
  9. Oxankle

    Oxankle Well-Known Member

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    Thanks, Agman:

    I sure am glad to hear that; I think I can find the contacts on the back of the tach--Sure does make the job a lot more simple.

    Now, let's see if I have to pull the whole cluster to get to the tach. Even if so that is not a big job, and my cheapie manual covers that.
    OX
     
  10. WisJim

    WisJim Well-Known Member Supporter

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    Two suggestinos regarding a manual for the truck. First, maybe the library has a copy or can get one, via interlibrary loan. Second, a Haynes manual may be available, and should be under $20.

    If you get a copy from a library, copy the wiring diagram and other pertinent pages.
     
  11. Oxankle

    Oxankle Well-Known Member

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    Jim:
    I have the Haynes manual for my truck but it does not cover the tach. It DOES cover removal of the instrument cluster, so when I get around to it now I will clean the contacts on the tach. I suspect that will do it as the tach works fine when it takes a notion to work at all.
    Ox