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Tachometer Advice

Discussion in 'GM 6.2 Diesels' started by joeq, Apr 9, 2016.

  1. EWC

    EWC Active Member

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    I have one of the cable drive units . I'm thinking one of the old Moroso 10,000 RPM cable drive tachs mounted right in front of the dash . On second thought , maybe not .
     
  2. joeq

    joeq Member

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    Mar 19, 2016
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    Will, thanks for those links. I see the Faria sender listed on Amazon, but don't understand it's mounting location. The Autometer video, clears up a few questions, but doesn't look financially pleasing. $150 for a tach, then, I don't believe it comes with the sender, then a scan tool to set it. Sounds like $300 when all is said and done. Then you'll have a scan tool to sit in a draw and never get used. I guess if it was a factory in dash tach, with an ESS that came along with it, I wouldn't mind paying it. But not for an aftermarket set-up.
    EDIT: I see the Autometer does come with the alternator sender, (or does it) so that may take a bit of the sting out of it. Still need the cheap $80 scan tool to set it. Wonder if the Auto stores rent them?
     
    Last edited: Apr 17, 2016
  3. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

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    ZEPHYRHILLS FL
    When you use the alternator to trigger the tach, it doesn't use a sender, but instead the raw stator output. Problem is with your truck, you have the old style alternator that doesn't have the raw signal wire since it's only a 2 wire plug for the regulator. You can crack yours open and add it in, buy one like yours for marine use that has the tach wire, or upgrade to a newer style alternator with a 4 pin regulator plug. For the other styles, you can add on a flying magnet and a speed sensor, drill the bellhousing and use the flywheel teeth to trigger a speed sensor, or some people have drilled into the engine and used the teeth on the pump gear to trigger the sensor. The cheapest one would be to get a cheap marine tach for a diesel, crack your alternator open and add in the tach signal wire, then hook that up. You can pick up a cheap alternator driven tach for well under $50, and if you're slightly mechanically inclined, you can do the alternator mod to add in the wire yourself fairly easily.
     
  4. Will L.

    Will L. Well-Known Member

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    Boulder City Nv
    @EWC can you show or describe its mounting to the engine?

    @joeq Call around places like summit racing. Like mentioned Leroydiesel.com sells the digital one, but I know you said no digital. Can you find out if that style uses an external p/u or if it is alternator fed?

    @THEFERMANATOR - can you watch this video? Does the guy in video describe it properly- any of the 3 terminals? Also, if going off the "a" terminal for the cs alternators to use instead of the 2 wires from ESS for tach and TCM what is the second wire? Ground? If so which goes where?

     
  5. FellowTraveler

    FellowTraveler Well-Known Member

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    Nature Coast
    PDF of gen/alt wiring.
     

    Attached Files:

  6. EWC

    EWC Active Member

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    Jun 14, 2008
    Will , it's just an oil pump drive that has a threaded body with the center setup for a cable drive that comes right up the center . Kinda like a speedometer silverbullet . Almost looks like a speedo cable would just screw into it . Got it off a military engine that I bought .
     
  7. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

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    ZEPHYRHILLS FL
    That would do it, you just need the raw stator output to run the tach. Then any alternator driven marine tachometer will work off of it. You would have to calibrate it, but I'm sure he could get it fairly close pretty easily.
     
  8. joeq

    joeq Member

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    CT
    Will, that was a very informative video, altho when the narrator was talking, I kept finding myself yelling out, "BRUSHES, they're called "brushes"! But it looks like a wire off the rectifier bridge is all that's needed to send the signal. I'm assuming the gauge will need a ground wire too, unless it's grounded through the mounting. (And maybe a 12 volt source for a light) And would that be considered a 4 pulse signal, same as the ESS?
     
  9. Will L.

    Will L. Well-Known Member

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    That's what I'm asking to. The guy doing the video didn't present himself as overly knowledgable, but knew more than me for the tach! I've rebuilt those alternators but never added a tach.

    My autometer uses two words for the light, and two for the tach itself.
     
  10. joeq

    joeq Member

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    Mar 19, 2016
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    2 "words" for the light? Is that Bolder city slang, or what?:)
     
  11. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

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    ZEPHYRHILLS FL
    If you go with the alternator signal, then you have to use a tach meant for it. Reason being is it will be close to 12 pulses per crank revolution. The alternator runs at roughly 4 times the crank speed, and the stator signal is 6 pulses per alternator revolution. You can always measure your pulleys, find difference to get your multiplication factor, then multiply it times 6 to get your tach pulses per crank revolution.
     
  12. joeq

    joeq Member

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    Thermo-frank, you seem to really know your stuff. Do you have a tach in your suburb?
    PS, what do people call you here anyway?
     
  13. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

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    My real name is Ferman. My 95 came stock with an alternator driven tach, but I will probably be changing this here soon. I also do gauge cluster work on electronic gauges.
     
  14. joeq

    joeq Member

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    OK then, I'll call you "Frank", to keep your secret.
    So "Frank", is there a reason you want to get rid of your alternator tach? Is it the factory set-up? Not sure how rare the 95 tach cluster is, but the 80s I guess are like gold. I'm thinkin altho the single wire off the rectifier would be simple, the gauge and calibration, maybe not so much. If I were to pay the price for a stock 80s gas tach, and find an ESS, I'm thinking I'ld have the factory look I want, get rid of my vacuum pump, install the 4 pulse ESS, and have an easy install, W/O needing calibration. What do you think?
     
  15. Will L.

    Will L. Well-Known Member

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    Ha! Should have been to "wires".
     
  16. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

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    The alternator tach will be ALOT cheaper, but if you can find a factory tach, you can always use the dakota digital box to trigger it via your alternator.
     
  17. joeq

    joeq Member

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    And what is the add on price of the Dakota box, along with the cheaper tach? Does it balance out, price wise?
     
  18. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

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    I think the box is around $125, but it would run an oem gas tach off your alternator.
     
  19. joeq

    joeq Member

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    Ouch. So would an ESS, right? Which would be the "thriftier" buy?
     
  20. Will L.

    Will L. Well-Known Member

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    It depends on your looking for the deal. Personally I like the idea of Ferman's about the gas truck's tach from a boneyard, then getting the box for $125. You should be done with all of it under $200, but have a nice factory look when finished. There's plenty of room behind the dash to mount the box so it would be out of the way also.

    One place to call for used is boyce equipment in Utah. Those guys do a lot of m1008 diesel trucks- they might have used parts you need. Good work from the 2 Ive seen come from there for anybody wanting a complete runner.
     

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