Common symptoms: A/C blows cold for a bit but then you hear a "thud" sound and your cold A/C is now blowing hot air out of the vents. When A/C is on and you change the temp control from cold to hot and back to cold, the air doesn't return cold but rather stays hot. It is possible that it is an issue with the blend door, or in this article's case, the blend door spacer servo. It is a ~$17 part depending on where you get