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Service Light 900

I own a 91 940T with 172,000 on th odometer. Needless to say it has been a FAB car. I now have encountered this wierd problem with the SERVICE LIGHT. It seems to come on at unexpected intrevals. Haven't really had a chance to see how far apart the intervals are but it seems to be around every 2000 miles or so, instead of 5000 like it has been. I did go up to a wider tire right before I started havin this problem. I now am running 225/55-16 right now which are just a small hair taller than the 205/55-16 but it seems to be that the mileage is still being caculated correctly. Well any help with this weird situation would be greatly appreciated. Thanks fellow bricksters!!








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    Service Light 900

    Brian S. sure is proud of his low coolant light! I haven't finished the wiring on the 944T yet.

    Don't get rid of the service light. Personally, I have become fond of that service light, the one that comes on at least twice a day for a few months because I forget to reset it.

    OK Joe, show me, your from Missouri. Write the mileage on a piece of paper and throw it in the glove box and record the mileage when the light comes back on then report back. I never tore into one but it is supposed to be a mechanical reset, not electrical. It churns off OD gears. I mash my reset a with a pen refill few times to make sure it is reset correctly.

    Lets see, side wall was 4.87mm, now 4.44
    Dia was 25.74 in, now 24.88 in
    Circumference was 80.88 in, now 78.16 in
    revs per mile was 783.41, now 810.68

    Ah, yes, so if the light came on at 10k, it is now at 9660 miles in reality
    for 5K it is now 4830.

    The S light comes on a little sooner, not too much though. BTW when the spedometer says you're going 65mph, you are really going 67. At 70, actual is 72.5

    I think someone else is driving your car while you are sleeping.
    --
    Tom F








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      Service Light 900

      How did you get the fiqures for the new tires that I have. The new tires are a hair taller and bigger so it would seem to me that there would be less revolutions with every mile because of the bigger diameter!!








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        Service Light 900

        My apologies. I had reversed the numbers. You really are from Missouri.

        Side wall was 4.44mm, now 4.87
        Dia was 24.88 in, now 25.74 in
        Circumference was 78.16 in, now 80.88 in
        revs per mile was 810.68, now 786.41

        Old tires 10,000 is now 9,700mi (Using rev per mi as a ratio, 786.41 x 10000 / 810.68 = 9700)
        Old tires 5,000 is now 4,850mi (786.41 x 5000 / 810.68 = 4850)

        With larger tires 65MPH reads 62.81MPH on the spedometer.

        If 225/50x16 were installed mileage and speed would be close to dead on.

        Ref, http://www.csgnetwork.com/tireinfo4calc.html This is a great site with many automotive calculators
        --
        Tom F








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    Service Light 900

    Hmmm... your service light sure sounds like a PITA. Here's what I would recommend:

    Pull you instrument cluster (easy), take the bulb out from behind the service indicator, and put it behind the (unused) engine coolant indicator:



    Then follow the directions in the FAQ to install a coolant level sensor that will activate your lovely 'new' lamp if you blow a heater hose, crack the radiator, etc. Drive on with greater peace of mind.

    That's what I did with my service light...

    - Brian '93 945T







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