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Is this a symptom of a bad SI battery?

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  • Gregs///M
    replied
    I've rebuilt well over 100 SI boards, here are my observations regarding SI board symptoms:

    SI board controls power and signal for tachometer, MPG gauge, temperature gauge, service lights, and OBC calculations. Fuel gauge, speedometer, odometer and indicator lights are not interfaced with the SI board.

    So any intermittent or non operation of tach, MPG gauge, temp gauge, or service lights is a definite sign your SI board batteries are failing.

    NOTE: Prior to troubleshooting or replacing your SI board batteries you should replace fuse 10, 12, and 21. These old fuses power the cluster and are known to develop micro cracks that can expand/contract depending on temperature.

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  • tom@kartboy
    replied
    UPDATE for my situation

    looks like the wires that run from the tranny up to the shifter(reverse switch wires?) were rubbing on the drive shaft and got burned through.


    soldered it up and swapped out for a new fuse (10?) and were good to go.

    Tom

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  • tom@kartboy
    replied
    Well we made it to bimmerfest and back without issues. Still cant figure out whats up. right now only the speedo and odo are working. no HVAC either.

    going to put it on the lift tomorrow and take a closer look. hope its something stupid or its gonna be pricey...

    Leave a comment:


  • Mick
    replied
    Is the OBC still displaying MPG ect..? If so you can press the 1000 and 1 buttons at the same time to display the fuel level in liters.
    Doesn't fix your problem but at least you'll know how much fuel you have.
    Good luck.

    Leave a comment:


  • tom@kartboy
    replied
    Bumping an old thread. This morning the car was fine. Washed and dried the car getting ready for Bimmerfest in SB this weekend. Leave the shop and no tach, no temps and no fuel level. Hvac is not working either. Ripped apart the dash and the SI seems to be ok. the batteries would show 3V. checked and moved around the fused but no avail. :( Wish me luck driving 200 miles tomorrow to Santa Barbara. The car seems to run fine. i'll just have to keep an eye on the odometer to see when its time to refuel. Should make for an interesting drive...

    Tom

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  • Steve88M3
    replied
    Well, the speedo is bouncy but functional. I'm more concerned with having a working tacho than anything else. I know its the yellow connector into the cluster that sends the revs, but I'm not sure if this is the culprit.

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  • mfanatics
    replied
    how about the sensor that is on the differential. just another area to look at. please correct me if im wrong.

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  • Steve88M3
    replied
    Yeah, my fuses are fresh (so fresh and so clean), numbers 11 as well as 21 I think were fine but I replaced them anyway.

    Any other idea guys?

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  • mfanatics
    replied
    in my situation i found out that it was the fuse that was causing the problem. I also saw a damaged wire under the car that might have cause a short to pop the fuse every once in awhile. Its the 7.5amp fuse that i am referring to.

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  • Steve88M3
    replied
    What was wrong with the connections on the back of the cluster? I just got my cluster back from an authorized VDO dealer and it still doesn't work.


    Its starting to irk me.

    Leave a comment:


  • UofOm3
    replied
    check the sauders on the connections... my dads m3 just had the speedo quit, and the tach was sketchy... the tech just fixed the connections on the back of the cluster and all is well... while they were in there they replacedthe SI board and bats.... might be a similar problem on your car

    Leave a comment:


  • dans m3
    replied
    How did you test the batteries? Out of the car?

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  • Steve88M3
    replied
    So....I tested by batteries and the gauge said they were still good.


    What should I do next? The fuses are fine and I'm stumped.

    Leave a comment:


  • jmarch
    replied
    You're probably right. When I disconnected my cluster for two weeks the tach and the temp gauge quit. I'd start by replacing the batteries on the si board.

    Leave a comment:


  • mfanatics
    replied
    Yes. I got a cluster that i believe was sitting for awhile. i am pretty sure its the batteries. What you think?

    Leave a comment:

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