Broken Fuel gauge..how to fix

i got an XT, my fuel gauge has been broken since i got the car, i'm not sure how to fix it, it's not the sender as i unplugged it to test if it had an effect but the dial didn't move, the problem is if i refueled the dial would raise up to the current fuel level..but it won't go down, i found this out when i stuck a wire in and pushed the dial to empty, it went back up when i turned the car on, turned car off and it is stuck at that level, what could the problem be..and how can i fix it?