Gas gauge / sending unit testing

You have your OLD sender and a good multimeter? Or is the new sender out of the tank? Use the multimeter on low ohms, to adjust to the "yellow" settings in the photo. These are lo (empty), mid (1/2) and high (full) readings on either oil, temp, or fuel. So you can cross check by setting the resistance to those three readings, and hooking it in turn to each gauge sender wire. Gauges should read as indicated after a few seconds.