Coolant temp gauge doesn't work

Does anyone know what the resistance should be on the coolant temp gauge sending unit at normal engine temp? I measured it at 100 Ohms. I also took the wire off the sending unit and placed it to ground, and the gauge didn't peg out at hot. So I'm thinking the gauge is bad. Do you think my diagnosis is correct?:dunno:

As long as it was a FOR SURE ground (ie get some alligator clips and wire it directly to negative battery post), and your needle didnt go passed the hot mark, then yes your gauge is bad.