Oldsmobile/Buick Repair: engine coolant fan, olds cutlass supreme, olds cutlass

Question
96 Olds Cutlass Supreme 3100 engine. I was idling with A/C off and notice the engine temp climbing. I opened the hood and neither fan was running. What I did was turn the A/C on and one fan was running then and gradually cooled down. When I start the car cold,  I have seen both fans come on, so I know its not the fans themselves. I have ruled out the controllers(relays) by unplugging them each while the fan is running and the fan starts and stops with plugging in and unplugging relay from box. I think it may be the temp switch not turning the fan on with high temp. I found the temp sensor near the thermostat under the throttle body) with three wires. Is this the correct one to replace? I would think that the radiator temp would be measured for this purpose, but the only sensor on the radiator that I can see is near the trans cooler and I would think that it is for that purpose.I do have an engine temp gauge in the dash.

Answer
Hi Phil,
I believe that sensor in the radiator is a coolant level sensor.
The one near the thermostat should be the one that sends the signal to the ECM, which operates the relay.

Here is a link that tells how the sensor should read.

http://www.chevytalk.org/threads/showflat.php?Cat=0&Number=1685353&an=0&page=0#P...

Van