’85 308 QV speedometer swings and intermits | FerrariChat
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’85 308 QV speedometer swings and intermits

Discussion in 'Technical Q&A' started by cecinestpasunjan, Jul 21, 2006.

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  1. cecinestpasunjan

    cecinestpasunjan Karting

    Sep 15, 2004
    51
    Frankfurt, Germany
    Full Name:
    Jan
    #1 cecinestpasunjan, Jul 21, 2006
    My latest problem… and yes, I searched the archives :)

    When I start driving speedometer / tachometer are both working fine. After 20 minutes or so the needle starts swinging around the actual speed. The swinging amplitude increases slowly and then the needle gradually slips down to zero. At this point the odometer stops as well.
    The problem is reversible because the instrument works again after some time with the engine turned off but the problem reoccurs during the next drive.

    A search in the archives revealed that the speedometer sending unit might be the likely cause of the problem. Do you agree or are there other possible causes? If so, how can this be diagnosed? Does the unit always have to be replaced or are problems such as the one described above sometimes caused by things like misadjustments or dirt.

    The respective spare is no longer available via Ferrari UK. Does anybody have a cross reference to another car type or the part number / name of the OEM supplier so that I can buy the sending unit in Europe?

    Best regards
    Jan
     
  2. cecinestpasunjan

    cecinestpasunjan Karting

    Sep 15, 2004
    51
    Frankfurt, Germany
    Full Name:
    Jan
    #2 cecinestpasunjan, Aug 19, 2006
    For the records,

    Speedometer is working again after having replaced the sending unit.
     
  3. tvine

    tvine Formula Junior

    Jul 19, 2006
    270
    Cadillac, Michigan
    Full Name:
    Tom Vine
    #3 tvine, Aug 19, 2006
    I had a similar condition with my '79 308GTB. The speedometer would work off and on. Based on advice of a speedometer shop in the Twin Cities (I don't remember the name but could look it up) I tested the sending unit with an analog amp meter watching for needle deflection as it was spun quickly by hand. I got no needle deflection so I replaced the sending unit (pulse generator). Works fine now. You may be able to check yourold unit but it sounds like you have the problem fixed.
     

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