Key on/helper in the drivers seat, you at the sender, pull the L shaped connector off of the sender threaded nipple & with a jumper to get in the female connector, ground it to a KNOWN confirmed ground & have your helper holler if it swings over to the F side & have him holler when it is almost all the way to the F so you can pull the ground. I like to ground it all the way up front to the batt neg post with some jumper cables to CONFIRM I'm doing a legitemate test. With the connector still off of the threaded nipple, ohm the threaded nipple to the circular round sender metal flat base.