Ambient Air Temp Sensor

2002 Grand Prix GT, 3.8L. My ambient air temp continues to read erratically. I have changed the sensor twi, first time in May '06 which seemed to work for awhile. Then I changed it again in June '07. This last time it didn't seem to correct the problem. Sometimes it reads fine but then it starts to go up or down and seems to reverse itself when it reaches a certain point. Weird. Anyone have any ideas what could be causing this. Hate to spend another $10 to replace it again. I've sprayed the electrical contacts but not sure where the wiring goes to from the sensor. Maybe another circuit problem somewhere. Haven't really noticed any problem with A/C - blows nice cold air whenever needed (I'm in Fla). Any thoughts would be appreciated.

I would inspect the wiring to see if you have any spots worn through where bare wire is showing or has gotten corroded.