a/c fan not operating properly

Your vehicle is equipped with a Blower Motor Power Module which is controlled by the Body Control Module (BCM) from various inputs from the Powertrain Control Module (PCM). You also have a Sun Sensor located on the top of the instrument panel. Make sure this is not covered by anything . The sun sensor is a photo diode. For this reason the sun sensor responds to sun light intensity rather than temperature. It is used to aid in determining proper mode door position, temperature door position and blower speed. The sun sensor is also used to sense day/night conditions for automatic headlight control if so equipped, and has an LED indicator for the vehicle security system. Other factors which may affect the blower operation are, Ambient temp and Engine Coolant temp sensors.