Saturn Repair: Guage not reading overheating problem, radiator hose, fan sensor

Question
Hello..I have a 99 sl2..It already has 120,000 miles(not fr me). When I bought the car(1-1/2yrs.ago), we had to change the water pump and radiator.Everything was fine but now it boils over and the temp guage is reading between 0-1/4 the whole time so the fan doesn't come on(w/AC it does).2x in one day it over heating. I changed the pressure cap..seemed to be working ok(still no temp reading change).Next day flushed out radiator(overdue). The cleaning stuff was in the radiator going on a day..so far so good..All this time still managing to get to/from work without embarrassment of smoke billowing out of my hood.Then last night got stuck in a damn drive-thru@wendys and while I was leaving it started smokin again..Again pulled over waited awhile and added water to make it home. Could it be the fan sensor,thermostat,cooling fan sensor(Trying all the reasonable answers 1st)money wise :)
                  Much Mahalo for your time,JMAlvarez


Answer
Michele,
 Go ahead and replace the ECT sensor (also called the PCM Temp sensor).  You will find it on the driver's side of the cylinder head, under the radiator hose.  This sensor tells the computer how hot the coolant is, when to apply the fan and so forth.  I would bet you money that is the problem...especially if the fan motor works when you turn on the A/C.  I'll bet you dollars to doughnuts that this will fix your problem.

Chris