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    tachometer question

    hey guys my tachometer stops working after at most ~2 minutes of starting the car and then the inspection light starts blinking. with the tachometer dies mpg gauge also.

    the first thing that came to my mind was SI board batteries. at first it made sense as I figured the fact that tach works fine everytime i start the car indicates that batteries retain some charge while the car is off. also i noticed that the amount of time tach works after car starts is decreasing.

    i searched the forums but couldn't find a case where tach first works for a while every time then stops. everything else is working on the cluster. can it be the batteries? any suggestions is appreciated.

    if it's the batteries, do you know if all SI board batteries are soldered? i have a 89 325i if that helps
    ahmet

    #2
    SI board batteries would be a good place to start. As far as I know they are all soldered in.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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      #3
      jlevie thanks for the suggestions. i'll try to give it a shot this weekend. what i don't quite understand is why only the tachometer stops?

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        #4
        You said the MPG gauge also dies... The signals for both instruments pass through the SI board.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

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          #5
          alright i finally pulled my cluster out and here's what the SI board looks like:



          it's more or less what I expected with the exception of the smaller circuit board holding the batteries. all other pictures i've seen have the batteries directly mounted on the SI board but mines are on a different board standing off from the SI board. here's some closer shots:




          before I attempt battery replacement (may be a destructive repair) i wanted to ask you guys if you've seen this before. also batteries have board mounting tabs, are these usually welded or soldered to the board?

          i'll check the battery voltages as soon as i replenish my multimeter's battery.

          Edit: sorry for the out of focus pics

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            #6
            so i checked the voltage reading on both batteries, they are both 3.22V. i'm not sure what this means as far as remaining battery capacity. any ideas?

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