Why is the fan, air conditioner, heater or windshield defroster not turning on?

If the blower is not turning on at all, check the related fuse.If good, check for power at the fan motor itself with the fan "on". If power is there, then the motor may be failed. If no power, check the blower resistor or switch. There is also a blower motor relay in the powertrain electrical box under the hood, this is also somewhere to check.