Best ground strap location

Discussion in 'Troubleshooting & Diagnosis' started by Chintzel, Jan 21, 2017.

  1. Chintzel

    Chintzel Veteran Member

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    Hi all, so I finally got my tachometer professionally serviced and according to documentation, it's working perfectly. However when I reinstalled it into my instrument cluster and connected everything up, the engine starts right up but the tach only reads about 500. When I rev it to about 3000 it seems to only go just above 500 and bounces around there. I think my ground is not good. Where's the best place to attach it? Should I attach it to the back of the tachometer or to the fuel gauge? My car by the way is a 1971 RS with optional gauges. Thanks
     
  2. wnmech

    wnmech Veteran Member

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    Do you still have the points distributor and coil? I'm not sure about where my 71 instrument cluster is grounded but my U-14 factory tach uses a brown wire and it goes on the negative side of the coil. Just something to check until someone with the wiring diagram chimes in.
     
  3. Chintzel

    Chintzel Veteran Member

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    It has HEI ignition.
     
  4. Hey G

    Hey G Veteran Member

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    Is your engine grounded to the sub-frame?

    G
     
  5. Chintzel

    Chintzel Veteran Member

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    Yes it is. Before I did that I had all kinds of problems.
    My current issue is that after I swapped out the resister on the back of my fuel gauge, which now seems to be working OK, the tach went out. I suspected the tach was bad and sent it to the tachman who did indeed find it was kaput and fixed it - it's working fine on his bench set up. Before this, Before this the tach did not work at all. Now it registers but won't rev much above 500.
     
  6. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

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    .


    I never use the chassis for a ground, I always home run the battery.
    Much more reliable!!!


    .
     

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