Tach help needed.

Electrical & Ignition

  1. bee71

    bee71 Well-Known Member

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    Recently the tach on my 71 Bee started to not work on start-up. Then after driving for a while it would work. It always has been 1500 rpms too high when working but the intermittent has me stumped. Also, previously when shut down the needle would hover at 500 rpm. Now sometimes when I get in the car, I noticed the needle parked at just under 0. When it is like that I find that that is when it won't work on start-up. Do I have a current drain when the needle is at 500 rpm after shut-off? Is the blue wire that is attached to a clip and protruding stud coming out of the engine side of the firewall and outer fuseblock the tach wire?
     
  2. A383Wing

    A383Wing Well-Known Member

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    if you did nothing to car or tach between it working right back then and now, sounds like a resistor or capacitor inside has gone bad..time for a rebuild or new circuit board inside
     
  3. The Horvaths

    The Horvaths Well-Known Member

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    At the very least, it may be time for a tech to check it out.
     
  4. dangina

    dangina Well-Known Member

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    • The Horvaths

      The Horvaths Well-Known Member

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      Good info, dangina.
      If you're an electronics nerd, like me, it's easy to accurately calibrate a (working) tach with a (12V) pulse generator. For an eight cylinder, it's Hz/8*60.
       
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