Pulse Width Modulation:  This is our method to control the fan RPM that will control the temperature of your radiator.  

 

The fan RPM is linear to the temperature of the sensor.   Therefore, when the thermostat opens and warm to hot coolant starts to flow out the radiator, then the fan or fans will start to spin slowly.  

 

When you start a cold motor, with our Auto Cool Controller installed, the fan or fans will not start to spin until the sensor on the OUTFLOW port starts have warm coolant heat it up.

 

As the engine and radiator gets to operating temperature, the fan RPM will increase.  The sensor measures the outflow port in real time and adjusts the fan RPM as required.    This technology is not Digital but analog to pulse width modulation using modern solid state devices.

 

At freeway speeds, your fan or fans should be at zero or very low RPM with the high amount of air- flow into the radiator.