2005 GMC Yukon front fan blower intermiitent

They have issues with blend doors not working.
Those actuators have small plastic gears inside and 1 chipped tooth or small crack leads to erratic operation. If you remove the actuator take the darn thing apart, and at the same time you can manually work the door to see if your symptoms change. But before dissassembling, discconnect the battery for a half hour, this will reset the bend door operation. However, depending on your radio, you may need a code to reset the radio.