temp gauge prob

[4montecarlo]

my temp guage started acting up last week. the gauge went full hot. so i replaced the sending unit in the head, no change. I disconnected the electrical wire to sender, and the gauged dropped to the middle. i then pulled the gauge cluster and ran new wire from sender to gauge, and again gauge went full hot. I assume the prob is the gauge itself, is that correct? can i fix the gauge by itself or do i need a whole new cluster?
thanks
matt