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    Tach Swap Unique problem

    Hi,

    I have used the forums for a long time now and registered a while ago, but this is my first post.

    I have a model 1987, September 86 build 325es. I chipped it and have been trying to swap the tach for a 7k tach. My gauges cluster is a motometer cluster which uses the newer style tach (very small pcbs on back). Initially I tried with out any research to put a VDO set in from a 91 318i which did not work.

    I then read the often referenced strictly eta tach article and found I needed one from an 87+ is.

    I just tried putting in a motometer tach from an 89 325is and retained my original coding chip (the one on the front), and it reads 0 at idle and then will bump to 1000 at engine speed of about 2k. From there it becomes off exponentially.

    I have read hundreds of threads about tach swaps and have never come across this. Any help is greatly appreciated.

    Thanks

    #2
    Get an I cluster, put in your coding plug and your original fuel gauge. Done.
    Mtech1 v8 build thread - https://www.r3vlimited.com/board/sho...d.php?t=413205



    OEM v8 manual chip or dme - https://www.r3vlimited.com/board/sho....php?p=4938827

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      #3
      Thank you, I have been trying to figure all of this out for months.

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        #4
        should have asked sooner.
        AWD > RWD

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          #5
          The last tach you tried should have worked. Unless the tach happens to be bad, the improper operation could be a bad SI board or a bad tach output section in the DME.
          The car makes it possible, but the driver makes it happen.
          Jim Levie, Huntsville, AL

          Comment


            #6
            The last tach you tried should have worked. Unless the tach happens to be bad, the improper operation could be a bad SI board or a bad tach output section in the DME.
            My original tach worked/works fine. I suppose the tach I bought could be bad, I don't have any good way of finding out though. As far as the SI board goes there is no damage to it due to leaking batteries, it appears to have been replaced a while back. Also since I reset my service indicator it properly counts down the lights now.

            should have asked sooner.
            Yes I should have but I figured I would try swapping just the tachs first.

            What specific part is it that makes the needle sweep differently from 318, is, or es? If I could narrow this down I may be able to put a cluster together from some spare parts I have around. When comparing the main PCB from the 318 VDO set I have to my original the only difference I found was: a capacitor which links two solder points in the middle of my original cluster, whereas on the 318 cluster there is just a wire, however this seems to be related to the speedo which is bizarre because I swapped that speedo into my cluster.

            Also if I am not mistaken VDO parts are interchangeable with Motometer correct, as I have swapped a VDO speedo for the original Moto?

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