That sensor has no effect on the air conditioning. Where are you located? If you are in a region where it is summer right now, then it seems to me that your engine cooling system is not working properly. If you are sitting at idle, less air flows through the radiator cooling fins -- much less than if you are in motion. With an engine that is too warm, you won't get cold air from the A/C vents. Check that your electric cooling fan is turning on when your air conditioning is running.