A cooling fan clutch clutches your engines cooling fan on and off. The engagement of the cooling fan is dependant on the need for more or less cooling air to flow through the radiator. The electronic fan clutch is a thermostatically controlled device that when operating in the proper manner, varies the fan speed independently of the engine speed to maintain the optimum coolant temperature.
When traveling at highway speeds, with moderate outside temperature, the fan should idle along, turning just fast enough to add a little air flow when needed to meet the current cooling requirements. In this manner, the fan noise and drag on the engine are significantly reduced. When reducing speed, the fan clutch will sense higher temperatures through the radiator and engage in increasing fan speed and help maintain constant engine temperature. It may, in fact, cycle as the temperature of the air through the radiator changes, depending on airflow.
If the fan clutch operation is normal when first starting your vehicle, the fan clutch should properly engage, and the increase in noise and airflow should be noticeable. After about 60 to 90 seconds of engagement, the cooling fan clutch should then disengage, and the noise and airflow will be reduced. The fan will continue to turn but at a much-reduced speed. As the engine warms up and the coolant temperature rises your thermostat opens. The engine coolant will now move under pressure to the radiator to regulate the engine temperature. The fan clutch will sense this and increase the speed of the fan to maintain a normal operating temperature.