One terminal of the sender connects to the plate that mounts to the tank--this is grounded because the tank is grounded. So, polarity is involved here. I can remove the tank ground and switch the wires.
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 5, 2015, at 1:06 AM, Josh Muckley <muckl...@gmail.com> wrote: > > 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 > <$_3.JPG>
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