What conditions trigger radiator fan?

[pcohen15]

I live in AZ, so it's 100+ five months of the year. My car's temp is always where it's supposed to be, regardless of ambient. I run A/C all the time.

I might be nuts, but I think my fan is running more this year than last. And at at a pretty high speed, based on the noise.

So I'm wondering, what conditions cause the fan to run? Is there something that might not be working correctly that would cause the fan to run all the time? I've had the car for 16 months and it seems to run more than a year ago.

Would like to know how other hot weather cars in AZ, CA, and NV behave when it comes to their fans.

Thanks.

[decimation1]

If I remember correctly it's a multitude of factors....

Ambient temp
vehicle speed
a/c pressure
coolant temp

and I might be missing one or two others

[deansbimmer]

It's a Pulse Width Modulation fan (PWM/variable speed). The DME controls the speed depending on needs, so the speed will vary. You may only hear it when it goes full speed, so you're probably not able to accurately compare its current duty cycle to previous years.

A/C use will turn on the fan as well but will still run at varying speeds as engine temps and refrigerant pressures demand.

[pcohen15]

Originally Posted by deansbimmer

It's a Pulse Width Modulation fan (PWM/variable speed). The DME controls the speed depending on needs, so the speed will vary. You may only hear it when it goes full speed, so you're probably not able to accurately compare its current duty cycle to previous years.

A/C use will turn on the fan as well but will still run at varying speeds as engine temps and refrigerant pressures demand.

Thank you. I'll stop worrying now.

[pcohen15]

Originally Posted by decimation1

If I remember correctly it's a multitude of factors....

Ambient temp
vehicle speed
a/c pressure
coolant temp

and I might be missing one or two others

Thank you!