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tach wiring??

Discussion in 'Early CJ5 and CJ6 Tech' started by gte636p, Nov 19, 2005.

  1. Nov 19, 2005
    gte636p

    gte636p Member

    smyrna, Ga
    Joined:
    Sep 23, 2002
    Messages:
    492
    welp, i picked up a tach today and went to wire it up. four wires showing out the back (red, black, white, and green). i know white and black go to the light on the inside (i took it apart). so red and green go to forming the tach peice of the unit. one feeds the turning mechanism, i think it's red. so where does the other go? back to ground or what? it seems like it should just go back to ground on the wafer board, but it doesn't... any advice on the last wire would be helpfull.

    also, i seemed to have hooked the last wire to the battery and that seemingly caused a stumble int he jeep and then death. starting fluid down the carb won;t crank it back up, the cap has good leads and everything. could accidently feeding 12V reverse through the tach output fry the ignition module on an hei distributor??
     
    gte636p, Nov 19, 2005
    #1
  2. Nov 19, 2005
    neptco19

    neptco19 That guy....

    Athens, GA
    Joined:
    Sep 26, 2003
    Messages:
    1,381
    Sounds like the red goes to 12v and the green goes to the coil. I'm 99% sure it hooks on the + side of the coil (been awhile since I hooked one up).
     
    neptco19, Nov 19, 2005
    #2
  3. Nov 19, 2005
    sparky

    sparky Sandgroper Staff Member Founder

    Perth, WA
    Joined:
    Sep 20, 2002
    Messages:
    9,221
    Hooks to the "Tach" terminal on an HEI. ;)

    Oh, and that sounds right to me. I have a green wire going to my dist.
     
    sparky, Nov 19, 2005
    #3
  4. Nov 19, 2005
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
    Joined:
    Nov 6, 2002
    Messages:
    4,275
    You'll need a "hot" wire and a ground to make the lighting work, and also a wire that's "hot" when the ignition is on. The last wire is the (-) side of the coil, this is what senses the engine RPM (or more correctly, how many times the points open and close.) In the case of the HEI, this last wire should be the tach wire off the distributor as Sparky said.
     
    w3srl, Nov 19, 2005
    #4
  5. Nov 19, 2005
    springerfever

    springerfever Member

    suwanee, ga
    Joined:
    Aug 1, 2005
    Messages:
    273
    amazing..seems like we've got close to the same problem! Mine's listed in the Intermediates.......

    good luck with getting yours working !!
     
    springerfever, Nov 19, 2005
    #5
  6. Nov 20, 2005
    dauntless_powered

    dauntless_powered SUB COB 2024 Sponsor

    Groton, CT
    Joined:
    Nov 3, 2003
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    1,000,081
    green should go to coil, atleast thats what mine does on my aftermarket tach
     
    dauntless_powered, Nov 20, 2005
    #6
  7. Nov 20, 2005
    speedbuggy

    speedbuggy Looking for a Jeep now

    Living the Good...
    Joined:
    Jul 1, 2004
    Messages:
    1,270
    What is the brand name on the tach? Have you tried to download the wiring diagram for it? The green wire in mine goes to the coil, but yours may be different.
     
    speedbuggy, Nov 20, 2005
    #7
  8. Nov 20, 2005
    70CJ5

    70CJ5 Member

    Pleasant Hill, Ohio
    Joined:
    Dec 11, 2004
    Messages:
    114
    Red-Key on Hot
    Black-Ground
    White-Marker lights
    Green-Coil or HEI distributor

    Never seen one that wasn't but there is always a first.
     
    70CJ5, Nov 20, 2005
    #8
  9. Nov 20, 2005
    gte636p

    gte636p Member

    smyrna, Ga
    Joined:
    Sep 23, 2002
    Messages:
    492
    welp, that's how i had it... guess the unit is a dud. my biggest problem now is that the jeep won't crank since my little experiment.
     
    gte636p, Nov 20, 2005
    #9
  10. Nov 23, 2005
    dauntless_powered

    dauntless_powered SUB COB 2024 Sponsor

    Groton, CT
    Joined:
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    1,000,081
    just a stupid ? but did you hook everything back up the way it was?
     
    dauntless_powered, Nov 23, 2005
    #10
  11. Nov 23, 2005
    gte636p

    gte636p Member

    smyrna, Ga
    Joined:
    Sep 23, 2002
    Messages:
    492
    yup, took it a part and noticed a connection that looked bad so i resoldered it and it came to life (both the tach and the jeep). the down side to it is that it's registering 1100 when at 900 and 2000 when at 2500 according to my dwell tach. i turst the dwell tach to be accurate, so the new tach ain't stepping foot in the cj.

    the jeep just needed some time to recover?? it's been running fine since it died the first time...
     
    gte636p, Nov 23, 2005
    #11
  12. Nov 23, 2005
    ljspop

    ljspop Lurking Bronco Dude

    San Diego, CA
    Joined:
    Jan 29, 2003
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    394
    Check the back of the tach for a 4-6-8 cyl switch.
     
    ljspop, Nov 23, 2005
    #12
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