The sender doesn't have a polarity. It is just a resistance. Is this what the back of your sender looks like? Which wires do you have attached where?
Josh On Apr 4, 2015 10:49 PM, "Robert Boyer via CnC-List" <cnc-list@cnc-list.com> wrote: > When you connect the sensing wire to ground, the needle goes positive all > the way as it should do but it does not register the fuel level. > > I now believe that one gauge is working correctly because the needle moved > slightly positive when energized--but the tank is completely empty. > > The other gauge is hooked up the same way but I think the wires inside the > tank sender is reversed, which makes the needle go in the wrong direction. > I remove the ground from the sender and reverse the sender polarity > tomorrow. > > Wal, would I also have to reverse the power supply polarity on the gauge > to make it work properly? > > Thanks! > > Bob > > Bob Boyer > S/V Rainy Days / Annapolis MD > 1983 C&C Landfall 38 - Hull #230 > email: dainyr...@icloud.com > blog: dainyrays.blogspot.com > > "There is nothing--absolutely nothing--half so much worth doing as simply > messing about in boats." --Kenneth Grahame > > On Apr 4, 2015, at 10:40 PM, Marek Dziedzic via CnC-List < > cnc-list@cnc-list.com> wrote: > > Josh, > > This is certainly not sailing related, but if i remember it correctly, > they are all really ammeters (the current flowing through them creates the > magnetic field that moves the needle). > > Marek > > > > Josh Muckley via CnC-List wrote: > > All analog meters are just measuring the "voltage drop" across a > resistance. The key is to have the appropriate voltage input +12v. If the > +12v and the sensing line were reversed then the "voltage drop" would be > "negative" driving the needle to the empty peg. > > Josh > On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List" <cnc-list@cnc-list.com> > wrote: > > I thought they were Ohm meters. Anyway, I just Googled it to make sure, > and see a ton of pages on testing marine fuel sender resistance. > > Wal > > you wrote: > > I agree with your diagnosis. It's gotta be reversed polarity...of the > sense and gnd. Fundamentally the fuel gages are just voltage meters. They > respond proportionally to the voltage drop across the variable resistance > in the sender. I would disconnect the leads and use an ohm meter to > measure and validate the resistance of the senders. Switching the polarity > of the sense and gnd monetarily probably won't break anything. Before > doing so validate that your wiring looks like the attached picture. > > > > _______________________________________________ > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go to the > bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > _______________________________________________ > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go to the > bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > > _______________________________________________ > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go to the > bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > >
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