Do the radiator fans run when a car is running down the highway?

[ist dwa]

With out wiring up a light I am curious if the radiator fans run when going down the highway? Is it a restriction if they are, isn't the air flow across the radiator enough etc?

I have always wondered this?

Thanks in advance.

 

[Stapl3]

The 1g ECU has no control over the fans. 1G's have a sensor on the bottom of the radiator [where the coolant is already cooled], that turns the fans on at 185 and off at 172. I suspect you could drive through Death Valley with ambient 130F at highway speeds and there would be no reason for the radiator fans. The fans simply wont move the same volume air as driving 70mph.

I think the real question you're after is what MPH of the car moving forward will equalize what the fans artificially mimic.

The fan blades are physically there regardless blocking airflow, so yes they are a restriction to flow. Them spinning would be less of a restriction to flow as they are aiding in the airflow. Is it measurable, sure. Is it worth measuring, probably not much. Think of the flex-fans on old v8s, they will flex to be straight as the RPM increases as the theory there is the fan doing effectively nothing [becoming more of a restriction to radiator core flow] is more beneficial than pulling more air through the radiator.