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Voltage at Sending Unit

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  • Voltage at Sending Unit

    How many volts should you be reading when you attach a VOM to the hot lead on the sending unit?

  • #2
    About 12 volts, but might be better to read it not hooked to the sender.

    JDP/Maryland
    JDP Maryland

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    • #3
      quote:Originally posted by JDP

      About 12 volts, but might be better to read it not hooked to the sender.

      JDP/Maryland
      Explain that. I am confused. Also, if it is not 12V off the sender what am I looking at?

      Thanks

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      • #4
        If you read the voltage at the sender with the wire hooked up, you'll essentially be reading the voltage of a circuit between two resistors in series (the gauge's coil and the resistance in the tank) so WRT ground it will not be 12V. I'm not sure what it should be and in reality will probably depend on the fuel level in the tank. If you read it at the wire's terminal with the wire disconnected no current will be flowing so you should read something close to battery voltage.

        nate

        --
        55 Commander Starlight
        http://members.cox.net/njnagel
        --
        55 Commander Starlight
        http://members.cox.net/njnagel

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        • #5
          quote:Originally posted by bondobilly

          How many volts should you be reading when you attach a VOM to the hot lead on the sending unit?
          http://studebakermuseum.org/archives.asp

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          • #6
            My bad, I was think tach sender.

            JDP/Maryland
            JDP Maryland

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            • #7
              How in the world do you guys know which sending unit Bondobilly is talking about? I'm dumbfounded. I know my car has 3. I think ya'll is sikeck. oops, I mean psychic.

              '50 Champion, 1 family owner

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              • #8
                quote:Originally posted by BobGlasscock

                How in the world do you guys know which sending unit Bondobilly is talking about?
                'cause a fellow 56J Owner nose what anothur 56J Owner thunk even befour he thunk it ...that's how.


                [)]

                <h4>Last Man Standing in Studebaker Indiana</h4>

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                • #9
                  Measuring voltage at the fuel tank sender is basically a meaningless exercise, in that there is no "correct" value. It's going to be somewhere between 0 and 12 volts. If it reads zero, the sending unit is shorted to ground, or the wire from the sending unit to the gage is open, or the gage isn't getting 12 volts from the ignition switch. If it reads full 12 volts (i.e. within a few tenths of a volt of battery voltage), then odds are good that the sending unit is open, or is lacking a proper ground.

                  A much more definitive test is simply to turn the key on, have a helper watch the gas gage while you use a test lead to short the sending unit terminal to a KNOWN good ground, like the rear bumper. If the gage unit is good, and is getting power, and if the wire to the sending unit is also good, the gage will peg out full in a few seconds. Instruct your helper to holler when it pegs out so you can disconnect the test lead right away!

                  Now move your test lead to the round base plate of the sending unit. You have make a bright spot with sandpaper to get a good connection. If the gage slowly rises up to a value consistent with the fuel level in the tank, then the sending unit is probably good, and your real problem is a bad ground between the sending unit and the tank, or between the tank and the frame.

                  Note that fuel sending units don't normally fail abruptly, they tend to become erratic and intermittent first. I've posted lengthy posts before on repairing them, which can readily be done if there is enough left to fix.

                  Gord Richmond, within Weasel range of the Alberta Badlands
                  Gord Richmond, within Weasel range of the Alberta Badlands

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                  • #10
                    Here's Gord's previous post:

                    http://www.studebakerdriversclub.com...,sending,units

                    Very slick fix!





                    1964 GT Hawk R2 Clone
                    Oakville, Ontario.

                    Hamilton Chapter
                    See you at Niagara 2008 Crossroads Zone Meet July 18-20
                    1964 GT Hawk
                    PSMCDR 2014
                    Best time: 14.473 sec. 96.57 MPH quarter mile
                    PSMCDR 2013
                    Best time: 14.654 sec. 94.53 MPH quarter

                    Victoria, Canada

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                    • #11
                      Thanks, I will try that out in the next day or so.

                      I printedout your directions.

                      BG

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