What is the engine temperature that triggers the radiator cooling fans and what controls it?:confused:
Thanks, Prairie Son

Water cooling circulation is set by a temperature switch in or near the exit of the radiator.
Fan action is controlled by another temperature switch in the cooling circuit.

Have a look at these links :

Howstuffworks "Car cooling thermostate" (http://auto.howstuffworks.com/cooling-system8.htm)

And

Howstuffworks "Car fans" (http://auto.howstuffworks.com/cooling-system9.htm)