make a long wire with alligator clips on each end & 1 end on the batt neg post and scrape other end on sender flat circular metal & see if you have continuity all the way up front. You wouldn't wanna increase voltage. A parallel circuit would not reduce voltage (think of Nacho's bulkhead parallel bypass or visualize the drive around lanes on either side of the main checkpoint at a border crossing. You'd wanna resistor in series (in the blue wire if we're on the same page) but I think it'd be a nightmare of experimentation to get the right resistor but I dont know electronics so no firsthand experience. I kept my 5/16 sender which worked fine & soldered in a bung in the bottom of the tank for enough flow for my app (my adv was I had a new Spectra tank). EDIT on second thought a resistor in the blue line to ground WOULD reduce voltage that the sender sees