Ac is cooling on the passenger side only - 2006 Subaru B9 Tribeca

Your problem is most likely a low refrigerant charge.You can go to your local parts store and buy a can of refrigerant (R134a) that has a connector on the can .Connect the can to the low side of the a/c system (There are 2 places to connect to the a/c system this is defined as the one hose that is larger of the 2 as a general rule the smaller side being the high side) start the engine and keep checking the cooling vent on the drivers side and it will slowly get cooler throughout the system."Important" make sure it is cool enough(like the passenger side)you do not want to under charge it after you retain the desired temperature throughout the a/c system stop the engine disconnect charge line and replace cap do not use the whole can unless nessasary or use an additional can as needed if necessary but the thing is to not under or over charge the system.I am confident this will work.