Sometimes the Air coming out of the passenger's side is Cooler than the Air coming from the Vents on the driver's side. Most of the time the cause of this is the Car's Air Conditioning System is low on Freon. The Air Conditioning System in your Car is a Sealed System. The AC System will only be low on Freon if something is damaged or something comes loose. The only way to detect a Leak is with an Electronic Leak detector as Freon is colorless and odorless. The other way is to inspect the System components for Oil Residue. Some AC Systems will have a Ultra Violet Dye in the system and the Leak can be detected by a UV light. To determine if you are low on Freon you will need to come into one of the Stamps Auto Tire Pros. A Technician will Evacuate your Air Conditioning System. The will then Weigh the Freon Taken out to see if you are low. They will check to see if they can find any Leaks. If the AC System is low and a Leak is not found. The Certified and Trained Technicians will add UV dye to your system when they Recharge it. Over a short period of Time you will need to bring your Car back in for a Free AC inspection to find the Leak with a Ultraviolet Light. There are other Causes for your AC not to Blow Cold. A Clogged Cabin Filter will also cause this. Failing Electrical components will also cause this. Other Mechanical issues in the Dash can also cause your Air Conditioner to blow cool but not Cold Air.