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Thread: Aftermarket fuel gauge compatible with stock sender?

  1. #1
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    Question Aftermarket fuel gauge compatible with stock sender?

    The stock sender is 70ohm empty - 400ohm full and I can't find anything that fits that range. There's an adjustable autometer gauge but it says its range only adjusts up to 280ohm. Has anyone found anything?

  2. #2
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    I just realized there are two senders, one for each side of the tank and their values are averaged. If I were to connect them in parallel, this would put its resistance right in range; however, since the left side of the tank empties first, this won't work properly. At half tank, left side resistance will be 70ohm and right side 400 - which means a total resistance of about 60ohm - but a true half-tank resistance needs to be ~118ohm(235/2) to read properly. Series would be the correct way to wire them to get a true average, but obviously a 140-800ohm gauge isn't going to exist if I can't even find a 400ohm gauge. I'm probably going to have to build some type of averaging circuit for this anyways.

  3. #3
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    OK I think I may have come up with a solution. Run the two senders in series with a resistor in parallel. If I use a 300ohm resistor, this will net me a total resistance of ~95ohm empty and ~218ohm full. Any resistor will work as long as the total full-tank resistance is less than autometer's 280ohm limit, I choose a higher value resistor to get the most resolution. Guess I just needed to write this all down and let the ideas bounce around inside my head. Maybe this will help some other people looking to do the same.

  4. #4
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    Update for anyone that comes across this thread:

    I have my gauge wired up like I said - it works, sort of. The first half tank only brings the gauge down to 3/4, the last half goes down to 0. Haven't decided if I'm going to mess with it any more.

  5. #5
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    Quote Originally Posted by Liquidity View Post
    Update for anyone that comes across this thread:

    I have my gauge wired up like I said - it works, sort of. The first half tank only brings the gauge down to 3/4, the last half goes down to 0. Haven't decided if I'm going to mess with it any more.
    I was looking at this unit when chasing problems on my gauge. Think I fixed mine but if it end up still being a problem, i'll be buying one. I confirmed with the manufacturer that it will work with BMW sender values.

    http://www.aircraftspruce.com/catalo...iABEgKupvD_BwE

    S.F.

  6. #6
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    A dual tank gauge is definitely a good idea, but I have 5 matching gauges in my dash behind the stock glass, this would look very out of place for me.

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