Help with tach wiring

Discussion in '1974 Specific' started by erials, Apr 4, 2020.

  1. erials

    erials New Member

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    a little background. I had to pull my engine in my 74 Z to retrieve a poly lock that fell into the block. (Ugh!). I know I was careless and did not have a rag in the lifter valley while adjusting the valves.

    After putting the engine back in the car, I’ve got it running fine with a little bit of valve clatter that I’ll adjust for.

    My problem is that my tach no longer works. I’m running a breaker point distributor 1112148 that has a pertronix 1 in it. I’ve connected the pertronix black wire and the external condenser wire to the negative side of the coil and the red pertronix wire and yellow wire and black wire from the wiring harness (these 2 are connected together from the factory onto a single connector) to the positive side of the coil. Engine starts and runs fine but the tach doesn’t move any more. I must be missing another wire from the tach but I can’t seem to locate any wires that are not connected. Tried a search but could not find anything.

    Anyone running a pertronix in a 74 breaker ignition able to help me out on how the tach connects to the coil? Am I missing another wire or do I need to look for a short or broken wire. Has to be something I’m overlooking or messed up reconnecting the distributor. Help please?
     
  2. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

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    I am probably wrong, I thought the tach wire was brown, and attached to the coil
     
  3. erials

    erials New Member

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    Yes I read that but most of the posts were related to 78-81 cars. I couldn’t find a brown wire coming through the firewall so I thought maybe the earlier cars were different. I’m stumped at this point. I could pull the instrument cluster and try to back trace the connection but would rather avoid that if I can. Hoping someone here knows what I can look for under th3 hood or tell me if something I’ve connected is wrong. Thanks!
     
  4. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

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    this is for a ford, however, might be helpful
     
  5. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    Dave is correct.

    If it's a factory tach and harness for a gauge cluster. Brown, 20 gauge wire.

    My Haynes manual wiring diagram for a '74 doesn't show the optional tach wire in the engine compartment.

    <edit> I found it... There's two engine diagrams.. One for a coil/points and the other is for HEI.
    The second one shows a brown wire.

    Was the U14 instrument cluster standard in a 74 Z?

    My diagram shows the alternate wiring for a Z28 with or without a U14 cluster.

    If the car was converted to a gauge cluster from an idiot light setup. A new wire would have been needed to be run from the cluster plug to the engine compartment.
    In that case, it might not be a brown wire.
     
  6. erials

    erials New Member

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    My Z28 has the factory tach in the gauge cluster and was originally a points car. Pertronix was added to the points distributor by the previous owner. Tach was working fine until I disconnected the distributor to pull the intake off. Stupid me forgot to take a pic of the wiring before I took it apart. I know this has to be something simple and will keep looking fora brown wire that’s not connected but so far nada.
     
  7. twestrup

    twestrup Veteran Member Lifetime Gold Member

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    Nothing changes with the wiring of the Pertronix, brown tach wire goes to negative side of the coil
     
  8. erials

    erials New Member

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    Thanks - wasn’t positive it was the negative side. Thanks for clearing that up.
     
  9. erials

    erials New Member

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    Thanks for the help guys. Apparently I have a tach filter / condenser that the brown wire connects to. I found an 8 inch piece of black wire with a connection terminal on one end and bare wire on the other underneath the car on the ground. I looked at the opposite side of the filter / condenser and saw what appeared to be solder and a very small tip of wire sticking out of it. I made an assumption that something must be coming out of the condenser so I soldered the bare end of the black wire I found to the filter / condenser and attached the other end to the negative side of the coil and voila! I have a working tachometer again!

    Just for my own personal knowledge does any one know what the condenser looking thingy is supposed to be doing?
     
  10. mallard

    mallard Veteran Member

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    Radio static?
     

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