temperature gauge just suddenly stopped working in my jeep. it worked perfectly fine for the past year and now it only goes up and down wen i start it or it will move up after i turn the engine off. i have no clue why it would have done that. does anybody else know?

 

sending unit is probably bad

 

so how do i fix it? my jeep does overheat on the trail and it is a pain in the *** not knowing how hott it is. because i usually have to turn it off and let it sit halfway through for 5 mins and then i can go again. but i dont wanna ruin anything by not knowing the temp. also i just ordered flowkooler water pump and a new replacement electric fan cuz mine doesnt work so i wanna see the difference it made temp. wise. please help! thanx