Gas gauge going crazy
 

It started acting screwy yesterday.It moves side to side when parked and then sometimes it jumps to way past full,then go down below half full. There's around 3/4 in the tank because I just got gas yesterday,and it will go back to t3/4 and then jump around again. I'm thinking fuel sender assembly. Anyone else have anything they think I should check first?

Grounding wires at the back by the tank and then the sending unit mine did that for a few days I had left it parked for a week or so and I parked on a full tank got in it to drive it and it said empty then full then half a tank after about 3 days it went back to normal hasnt messed up since and I didnt have a chance to persue the issue!

should be able to test the sender with an ohmmeter.