To test the sender attach an ohm meter to the terminal and the base, stick the bulb end in a beercan full of water, then heat the beercan to boiling with a propane torch. There should be resistance when cold and little to none when hot. If there is no continuity the sender is bad.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.