meathead

i left the car running outside and i was doing stuff around it. for the first time i heard some kind of fan (fairly loud) turning on and off. anyone know what this is?

AirlineMuseum.c

probably the A/C compressor

TBone2004

For real? That's the engine fan. Used to be running anytime engine was on for old cars, now it cycles on and off as necessary with newer cars.

detroi_TL

The cooling fan(s). They will cycle on/off depending on coolant temperature and/or ac head pressure.

jeda_zelda

Could someone who has a factory service manual pos the hi/on & low/off temps that should activate/deactivate the fan? This fan noise caught my attention back in the winter and made me start to think something was wrong - but the car has been running fine. If the sensor that reads the cooling temp goes bad, would it just stop working or could it possibly cause the fan to go on & off too much? Just a thought.

prophet_RENAMED

As everyone said, this is the radiator fan. Without airflow the radiator would saturate with heat and then your engine would start overheating. If you don't notice your engine temps rising when your car is at a standstill and running, then it's doing its job.

You can usually tell when the thermostat or fan is broken if your car is running and you stop at a red light and then notice the temp of your car goes up (and not hearing the fan of course).