1997 Saturn SC1 cooling fan temp sensor

I replaced the temp sensor with one from advanced auto parts $11.00 the cooling fan doesn't come on it just sits there and over heats. If I unplug the temp sensor the fan comes on immediately or if I turn on the air cond. It stay on as it should. The sensor harness reads 5 volts in and out when the engine is cold, as the car warms up the out gets down to about 1 volt. If I ground the relay the fan comes on as well, Im lost as what to do next, Thank-you for your valuable time. Alex