well when u first start ur car and is cold the neede should b all the way down so just look at it until u see the needle move up and at the same time try to feel and hear ur engine so u can tell when the engine is normal temp good to go. if u feel/hear the engine ready to go and the needle doesnt move then i dont think is the sensor, if the sensor was the problem the needle would move on a way u would notice like fly up or down or other things like it. like they said the needle should move up and stay under halfway/red line always.
does the gas needle is supposed to go down when u turn ur car off? i think mines did once now it doesnt, i think it is supposed to cause every other needle goes down when car is off