Is this the sending unit??

I changed the fuel pump a while back and after i got done my gas guage read way past full so I took the pump back out and looked for anything i might have messed up. Well I turned the car on again and this time the car read empty. So I crawled under the car and disconnected the wires that run under the car from the tank and unplugged it reads past full but when I plug it back in it reads empty. Anyone have any ideas on what might be wrong here.

check the float, no kidding, mine was doing it last night, the float fell off of the thingy, put it back on this afternoon, works like new