'84 240 tach

Discussion in 'Volvo 240' started by tom callaway, Aug 8, 2007.

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  1. tom callaway

    James Sweet Guest


    All Volvos worldwide came with Bosch alternators until the early 90s when
    some got Denso units.

    I wonder if the tach just measures ripple on the alternator output.
     
    James Sweet, Aug 11, 2007
    #21
  2. tom callaway

    jch Guest

    _____
    Jacob/James,

    That is exactly what it measures. Thus, since the the alternator revs
    are proportional to engine revs, the tach reports the proper value. I
    installed the tach back in 1985, and can't recall the details. There
    was sheet of paper that explained the hookup. I don't remember if the
    "W" terminal was mentioned. The brand of alternator does not really
    matter. A good Volvo dealer should be able to tell you the connection
    requirements.

    For what it is worth, there are after market tachs that derive a signal
    from the either the camshaft pulley or the fuel injection pump pulley.
    I believe they are used on some VW engines?
     
    jch, Aug 11, 2007
    #22
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