if the light isn't coming on, your okay. do you live in a cold environment? just because you had it idling for a while doesn't mean the fan is gonna come on. if your really concerned about it, revv the motor in neutral while sitting still, that should get the fan kicking. if your certain that your over heating, just jump the switch witha paperclip and the fan should go on. if the fan comes on that mean that your gettin' power and ground to the motor and obviously the motor works. with that test, you should be able to pinpoint wether it is a switch or fan. remember, make sure your overheating before you do this test or you'll be needlesly going to the dealership and they might just laugh at you. you can also test the sensor with a digital ohm meter but your going to need the specs of the switch.