Mack,
I am pretty sure it is a "90 ohm" sending unit for your fuel gauge. As the arm on the sending unit moves up or down depending on the fuel level, it changes the resistance (ohms) going to fuel gauge. Example: full tank is almost "no ohms" so the gauge reads "full". An empty tank, the sending unit is at "90 ohms resistance" thus making the gauge read empty.
As Eric stated: clean the connection at the spade connector first before driving or emptying the tank below the sending unit location. Hope this helps, Fred