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Odometer Problem

Discussion in 'Technical Q&A' started by RLK, Apr 15, 2015.

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  1. RLK

    RLK Rookie

    Apr 14, 2015
    1
    #1 RLK, Apr 15, 2015
    I bought my 308 GTSi with 26,400 miles on the odometer. I drove it a couple of times (less than 100 miles) and now the odometer reads 37,xxx miles. Worse, I noticed that, sitting in my driveway with the key on, engine running or not, the odometer advances ....click, click, click. Needless to say, I haven't driven it since.

    I thought the sender unit in the tranny was a magnetic coil and that the odometer just counts pulses, so I can't imagine anything that would cause this. The car has a new battery and the the cables are not marked with red or black. Could reverse battery polarity cause this or would that cause a lot of other chaos that would be very noticeable?

    Has anyone run across this before?
     
  2. alhbln

    alhbln Formula 3
    Consultant Owner

    Mar 4, 2008
    1,751
    Berlin, Germany
    Full Name:
    Adrian
    #2 alhbln, Apr 20, 2015
    Could be a defect of the Speedometer board or (rarely) a broken sensor. Try disconnecting the sensor connector in the engine compartment and check again if the ODO still ticks away while stationary.
    The sensor can be replaces (expensive) or repaired if broken: Veglia Borletti Speedo Sensors 68 1005, 68 1041, 68 0517

    You could also remove the Speedo from the dashboard and just wire it up with a 12V supply to check if the ODO runs without a sensor connected. Black is the ground wire, green the 12 plus wire.

    If the ODO counts in visible steps/ticks (12 per mile/km) then it is a type 1 speedo (early GTBi/GTSi), Palo Alto Speedometers has replacement boards for these. If the ODO forwards in small, smooth steps, then it is a type 2/3 speedo for which i am currently developing a new replacement board, this will take some more weeks. If you are unsure which type it is, post a photo of the type sticker on the side of the Speedo for identification.

    Good luck,
    Adrian
     

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