Temp guage
 

First off its a 95 sierra k1500 ext cab. short bed z71, when the truck is warming up the guage goes up to approximently 3/4 then drops back to just under halfway and goes back and fourth just over half ! if you shut the truck off for bout 5 mins the start it back up it reads 1/4 like its been off for long time but then repeats the process of going back up and coming back down ! I've changed the thermostat and cooliant still does this ! :confused:
Any help would be appreaciated ! Thanks