Fuel gauges

Discussion in 'General Electronics Chat' started by RFactor, Apr 6, 2011.

  1. RFactor

    Thread Starter Active Member

    May 1, 2009
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    I have been following a thread in the projects forum regarding fuel gauges and thought it was kind of interesting so am starting a new one here to discuss. It seems that years ago a fuel gauge in an automobile had a float in the fuel tank that moved a wiper on a wire wound resistor. The other end connected directly to the fuel gauge which was basicially a current meter. These older gauges were susceptible to movement caused by fuel sloshing in the tank although there were measurse to damp needle oscillation, it would never completely go away. In modern vehicles, the output from the variable resistor in the tank goes to the ECU (computer) The ECU looks at the input and calculates the what the actual level in the tank is. The ECU then sends the proper number of pulses to the stepper motor gauge. I have noticed that the gauge in my 2007 car is rock steady, doesn't matter if I am accelerating, stopping or rounding a curve. Even the once simple fuel gauge is computerized today.
     
  2. CDRIVE

    Senior Member

    Jul 1, 2008
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  3. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Almost all new cars (around 10 years or less) have stepper motor gages. Temperature, voltage, speedometer, oil pressure, tachometer, all of them :)
     
  4. RFactor

    Thread Starter Active Member

    May 1, 2009
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    3
    Thanks for the additional info Shortbus.
    CDrive, I was surprised like you were but after a bit of research and looking at how steady my fuel gauge is I realized things were different. I also noticed that when I turn on my ignition, the ECU steps all of my gauges to full scale and then steps them back down to the actual reading. So if you are having a problem with a gauge, checking that routine could be helpful. ie: if the gauge goes full scale but then goes to zero might be an indication that the ECU isn't receiving info from the send unit.
     
  5. debe

    Well-Known Member

    Sep 21, 2010
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    Thaught id post a computer driven instrument cluster made by VDO Australia & used in a Ford car here. It doesnt use stepper motors but crossfield drivers. The odometer can be put into diagnostic mode. You can then check quite a few instrument sensors & there resistance also can check fuel consumption.
     
    Last edited: Apr 8, 2011
  6. debe

    Well-Known Member

    Sep 21, 2010
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    More pics.
     
  7. RFactor

    Thread Starter Active Member

    May 1, 2009
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    Interesting pics Debe, things don't look anything like they used to.
     
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