Toyota Repair: What is the function of the water temperature switch, ground path, temperature switch

Question
I have a Camry LE 96, 4 cynlinder, automatic trans, A/C and I would like to know what is the function of the water temperature switch, which is located at the bottom of the radiator. I 've been trying to understand how the cooling system works. Thanks Ted!

Answer
This temperature switch is what turns the cooling fans on and off, it is a thermistor, it changes resistance with temperature, in this case the resistance between the two terminals is low, basically an open circuit at low temperatures and vey high at high temperature, there are also relays involved which will ground and the cooling fans will turn on when the resistance of the switch is very high(infinity)because of the high resistance(open circuit) there will be a path through the relay to ground and so provide a ground path to the fan which will then turn on because the other side of the system is always hot, all the switch does is make, or take away this ground path.
You can check this without the engine running by turning the ignition on and disconnecting the connector from the switch creating an open circuit, the colling fan will come on regardless of enine temperature, it may be a little hard to understand without looking at a wiring diagram but if you can give me an email address I can send you one.