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HEI Distributor- Tach wiring issues??

Discussion in 'The Hokey Ass Message Board' started by So-cal Tex, Aug 28, 2011.

  1. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 974

    So-cal Tex
    Member

    Guys,

    I did a search and came up empty....

    I have to admit that I am more of a traditional points type of guy ( wired many Tachs on my point cars) and this electronic ignition is foreign shit to me.

    I just installed a brand new Sun Retro Tach in my 55 chevy. I have the power wire connected to the electronic ignition switch ( seperate switch from the key), lamp wire to the headlight switch, ground wire to the body ground strap.

    When I flip the ignition switch ON the tach needle moves to the 0 PRM point which I presume is showing it has power, the light works, however I do not have the most important part the signal???

    DEAD TACH!!!

    I connected the signal wire to the only treminal left on the HEI distributor cap, but I am not sure it the right treminal for this wire.

    Anyone know where I am going wrong?

    Please help!

    Thanks,

    Tex
     
  2. badshifter
    Joined: Apr 28, 2006
    Posts: 2,690

    badshifter
    Member

    [​IMG]

    They usually say tach right on the cap. Only 1 place it can go.
     
  3. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 974

    So-cal Tex
    Member

    It is an aftermarket cap and that is the terminal I used ( only one left).

    Faulty brand new tach?

    Any other ideas?
     
  4. Mr48chev
    Joined: Dec 28, 2007
    Posts: 17,923

    Mr48chev
    ALLIANCE MEMBER

    The only way I know of to hook a tach to an Hei is on the Tach connection that Badshifter showed in the diagram above. Hooking it up any other way won't get you a signal.
     
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  5. 32SEDAN
    Joined: Jul 30, 2008
    Posts: 1,200

    32SEDAN
    Member

    Neg lead off of coil?
     
  6. Gman0046
    Joined: Jul 24, 2005
    Posts: 2,374

    Gman0046
    Member

    Negative lead off the coil won't work with an HEI. A friend recently tried hooking up his new tach that way and wouldn't work. He took it back and tried two other tachs and still inop.
     
  7. Hot Rod Chris
    Joined: Mar 31, 2011
    Posts: 456

    Hot Rod Chris
    Member

    Does it have a swith for 4,6, & 8 cylinders?
     
  8. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 974

    So-cal Tex
    Member


    Yes, and I put it on 8 cyclinders.

    Could the dist. cap be faulty? It is a cheapo from summit racing.

    Is there anyway to test for signal on that treminal to determine if the cap is faulty?
     
  9. jackandeuces
    Joined: Feb 20, 2006
    Posts: 825

    jackandeuces
    Member

    I just put a HEI in my 32 that had a 1967 point distributor with a retro sun tach...I called Sun to check on correct wiring they said that I only had to move tach signal ( think that it was green) from neg side of coil to tach plug on the GM HEI. .Works fine
     
  10. Gman0046
    Joined: Jul 24, 2005
    Posts: 2,374

    Gman0046
    Member

    I think thats exactly what my friend has to do. The minus side of the coil isn't doing it.
     
  11. 35mastr
    Joined: Oct 26, 2007
    Posts: 1,902

    35mastr
    Member
    from Norcal

    Make sure that you are actually plugging it into the pin. Make sure with a mirror that its actually making the connection and that it is not bent to the side.
     
  12. GMC BUBBA
    Joined: Jun 15, 2006
    Posts: 2,930

    GMC BUBBA
    Member

    Guys, the tach terminal and the negative terminal are the same terminal. If the car is running then all terminals are plugged in and operating. The only open terminal is the "TACH or negative coil terminal...
     
  13. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 974

    So-cal Tex
    Member

    I got it figured out.....faulty signal wire connection inside the Tach, damn Chinesse shit!!

    I re-crimped the signal wire and like magic I have a functioning tach.
     
  14. Gman0046
    Joined: Jul 24, 2005
    Posts: 2,374

    Gman0046
    Member

    SoCal-Tex, glad you figured it out. Now I'm really stumped. My friends car has had three different tach's on it hooked up to the minus side of the coil and none would work. If I remember correctly with the car off his rpm pointer reads below the zero line almost like it was driven there. My Chinese Mooneyes which works great reads right on the zero pointer with the ignition off. I wonder if that means anything?
     
  15. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 974

    So-cal Tex
    Member

    Gman, I am not sure how the other tachs work, but this sun tach is wired up on an ignition switch, so it only gets power when the car is running.

    When I flip the ignition switch ON ( gets power to tach) the tach moves to the 0 RPM, normally with power off it rests below the 0 RPM.
     

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