temperature sensor

[worldofme]

my temperature gauge on my dash is all !@#$&* up. the needle is pointing way past hot no matter if the engine is hot or cold and it stays in that position even when the engie is off. i was talking to my dad on the phone last night and he thinks maybe the temperature sensor has possibly gone bad and to check that. question is, I don't know where to look for. he said it could be somewhere on the side of the engine block and the only thing I can find like that is on the passenger side. my book for my blazer doesn't say anything about a temperature sensor.

so if there is such a thing as a temperature sensor, where should it be located and if not what could possibly be causing my gauge to be all screwy.

this is for a 1977 chevy blazer full