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fuel economy gauge on the blink

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    #1

    fuel economy gauge on the blink

    all,
    the fuel economy gauge doesnt work at low speeds...
    at high speeds, over 50 mph it works but either at the high end when crusing and then to zero when i let off the gas... so nothing in between...
    any ideas....??
    my cruise control is not working either... maybe the two are related??

    thanks for any info
    ~~~~~~~~~~~~~~~~~
    '90 325i sedan daily driven
    '85 325e coupe also a daily
    Tags: None
    #2
    when mine was recently not working, it was the battery on the service light board.

    the cruise control would be something else. check the brake switch at the brake pedal is out of adjustment or not working.

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      #3
      the brake switch was just replaced a few weeks ago.
      not sure why the brake switch would have any bearing on the cruise control or the fuel economy gauge.

      where is/what is the battery on the service light board????

      thanks for the reply btw
      ~~~~~~~~~~~~~~~~~
      '90 325i sedan daily driven
      '85 325e coupe also a daily

      Comment

        #4
        Pressing the brakes deactivates cruise control.

        Battery on the service light board is inside the speedo cluster.
        1990 325i
        2004 330i Individual 6-speed
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          #5
          The econometer issue is caused by the battery on the SI board. Mine was doing the same until I had the cluster rebuilt. Do your green/yellow/red service segments light up correctly when the key is in the on position before starting the car? If not, that's further confirmation that the batteries are toast.

          The cruise control problem is unrelated. That system only uses an input from the speedometer signal - everything else in that system is self contained. Check fuses, wiring connections and the brake light switch adjustment. When I got the convertible I damn near swapped every cruise component before I found a loose connection on the cruise control electrical harness under the dash.
          101

          The E30 collection:
          1987 325es M52 - Schwarz / Taurus Red Sport (son #2's)
          1987 325is - Delphin / Black Sport (son #3's)
          1987 325i Convertible - Triple Black
          1989 325iX Coupe - Diamondschwarz / Black Comfort
          1990 325iX Coupe - Sterling Silver / Grey Sport

          1981 Fiat 124 Spider 2000 - Green / Tan
          1998 Volvo V70 GLT - White / Tan
          1998 Volvo S70 T5 manual - White / Taupe
          2001 Ford Windstar - Silver / Grey (parts hauler)
          2006 Lexus GX470 - White / Tan (tow rig)

          Comment

            #6
            I confirm the SI board batteries will cause poor inaccurate operation of the econometer.

            Regarding the cruise control, make sure the single blue/yellow wire behind the speedometer is connected to the green plug. That is the speed signal output to the cruise control module.
            Owner - Bavarian Restoration
            BMW and European Electronics Repair and Restoration
            www.BavRest.com
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              #7
              wow guys,
              thanks for all that info... i will get on all that you've mentioned...
              i appreciate you all
              ~~~~~~~~~~~~~~~~~
              '90 325i sedan daily driven
              '85 325e coupe also a daily

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