There are two temp sensors on your car.
The CTS (coolant temp sensor [AC-Delco part #213-928]) for the computer (which also controls fan turn on) is in the end of the intake manifold, drivers side, just below the thermostat housing. Here's a picture of it
http://198.208.187.182/internet/View...Number=213-928
The temperature sending unit of the guage/light is located in the rear cylinder head, toward the drivers side, above the exhaust manifold.(AC-Delco part number 10232601) and here's a picture of it
http://198.208.187.182/internet/View...umber=10232601
The sensor for the guage has no effect on fan operation. Also, factory fan turn on temp is around 230 degrees for the primary fan, and the aux fan should kick in at around 240. The fans should kick on regardless of engine temp if the HVAC selector is set to MAX.