1987 cutlas cierra radiator fan

the radiator fan is not coming on and the car is starting to get hot. the fan does work as does the relay i have tested both. i think the fan coolant switch may be bad but i don't no the location of it and i can find it in any manuals. this is for the 2.8 v-6 any info would be gratly appreciated.

Look for a green w/white stripe wire going to a sensor looking device that's screwed into the block, a head or intake manifold at the coolant passages. My '86 2.5L had a "squeeze the sides" round pin connector.