With the sender grounded you should see an empty reading. With the sender disconnected you should see a full reading. Moving the sender through it's range, I would expect to see it go from 0 to 30 ohms, or close to it.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!